Your pH seems fine but I know that just under 7.0 pH is optimal for toms.

How many weeks old is the plant and how much fertilizer are you currently using? My first thoughts are either nutrient burn or pH problems. OR, this could just be from under fertilizing, so knowing the amount of nutes you have been using is vital.
Have you done any foliar feeding? Doing this can cause burns on the leaves when growing with HID lights. Always be sure to spray the leaves with nutrients only at night.

Also, this could be caused by a rapid fluctuation of pH. Has there been any recent large changes in pH of your nute solution (if anything above a 1.5 change in pH has happened recently, then that applies)?

What makes you believe that: "just under 7.0 pH is optimal for toms." - ethnobotany?

As far as I know the optimal range for hydroponic tomatoes is between 6.0 and 6.3. That's what I use and believe ideal. And on top of that I have 2 serious references that say exactly the same. Not to be confused with ideal PH for soil culture (as so often falsely transposed and/or misunderstood in this context).

As for the spots, either caused by deficiency or bacterial infection, it's too early/hard to tell for sure with just that "tiny sample pic" as "footing".

Magnesium, Zinc, Chloride or even "simple" calcium or potassium deficiency could start to show up like that in an early stage. Often deficiencies anyway come as a combination of more than one element being deficient or locked out somehow.

But just a few of these spots may as well just be a temporary "caused by some stress" and not worth the worries. Anyway, a few spots on a leaf aren't a good enough basis for any serious analyses. General growth, general aspect and health of the plant, roots, etc, should be considered.

If I had to give a quick and straight opinion though, I'd bet half of my money on Magnesium deficieny ;-)

@Lucas: Yes, I in fact did mix up the pH for soil and hydro regarding the tomato. Sorry!!! A thousand apologies.

If I had to guess though it would be with nutrients, as Lucas's detailed analysis states.

Maybe you should flush your system and then do your nutes again? This would at least give a starting point to deal with your problem. Hopefully both Lucas and I can agree on that : )

@ethnobotany,
Accepted, but actually no need to apologize formally, mate. It can/could happen anytime to me too. And in case I 'd hope to have got enough credit left to not get crucified up side down ;-)

The good thing about forums is that things can be corrected, - and in fact one must make the difference between correcting things and correcting people. Unfortunately, the bad thing is that some Fellas take things personally, no matter how you put them. Not you, as I can see ;-)

Topic: Not sure about the recommendation for a flush. That would depend on if there is use of media or not (resp. what kind of, and how much). Because if there is no media, there is not much to flush... as nutrients seem to get changed on a weekly basis.

Nutrients: The missing meter could indeed be an indication for "accidental" over- or under fertilization. Here one should at least have an idea about the actual nutrient strength in use.

About A.N. 3 part GMB: I can't say much about it, except that I don't like the slogans and rhetoric that are used to sell the product(s).

When reading among others:
"Plants suck down Grow-Micro-Bloom ingredients faster and easier so theyÂre fired up to give you fantastic growth and yield sooner and better."

This is indeed a very personal opinion and not to be taken judgmental, - but I don't want my plants to "suck down" nutrients and I don't want to fire them up either. With the choice of nutrients, I'd rather like them having a balanced and optimal nutrition, growing almost naturally and staying healthy.
I prefer to stick with nutritional facts, not with rhetorical "formulations". ;-)
Truth to be told, I have to give them credit about the work they did on the "phosphorus myth" and some other good jobs. But that doesn't cover up for simply overdoing it in MANY other fields, and not for the sake of the "Art", but explicitly for the dough.

@trenhes: More input, as in (at least) approximate nutrient concentration, general growth, general health, root condition, etc. is needed to get more of the bigger picture of what might have "affected" or just stressed these tomato plants.

Thanks Ethno and Lucas. Here's some more pics. Sorry for the size but I can't seem to make them bigger. The roots seem fine so I don't think it's too much nutrients. I was growing this in a 3 gal. bucket with 1.5 gal. of solution. Since my original post I put it in a 5 gal. with 3 gal. of new solution. The plant is 6 weeks old. Other than the spots the plant looks healthy, good growth and starting to bloom. I don't think I've had any major swings in ph. This is my first try with tomatoes, maybe I should stick with lettuce, much more forgiving.

Thanks again. I'll have to work on picture size. I'm using flickr, I might have to look to another site.

These pics might help a little more.
Overall the plant seems healthy

Thanks, Tod

Tod, your roots look great! Definitely not over feeding. If I was to take an educated guess, I would say Magnesium deficiency. You can foliar spray with epsom salt at 1Tbs. per gallon. Should see results in a couple days.

Thanks urbangardenfarmer. How often? Is the best time at night or does it matter?

Thanks, Tod

The symptoms showing only with older and mature leafs draws the deficiency down to the mobile elements.

Nitrogen
Phosphorus
Potassium
Magnesium
Sulfur

As nitrogen and phosphorus can rather be eliminated,
we have 3 left: Potassium - Magnesium - Sulfur

If you spray with Epsom Salts (as recommended by urbangardenfarmer), you will supplement with both Mg and S. But I would also insure that your nutrients have enough Potassium content, as it becomes even more vital with flowering.

Nutrient specs for tomato may vary with varieties, climate and growing rates as well. Some variety may be thriving (blooming and fruiting) with some "standard nutrient formula", while others may require (much) more Potassium in relation to the Nitrogen content.

The funny (but actually plausible) thing here is, that the better and quicker your tomato grow, the more demanding they get about optimal nutrition. Except some "Dutch greenhouse varieties" that produce high yield with a more standardized (and cheap) nitrogen focussed formula. Well, as we know those are RED, perfectly calibrated, early, high yielded - but taste like water ;-)

Here is a typical tomato formula that may still vary with type and climate, but gives you a good idea of actual elemental requirements:

N- 150-170 ppm
P- 35-50 ppm
K - 200-250 (280) ppm
Ca - 150 ppm
Mg- 45-50 ppm
S - 55-90 ppm
Fe- 2.8 ppm
Cu- 0.2-0.25 ppm
Mn -0.8 ppm
Zn -0.3 ppm
B- 0.7 ppm
Mo -0.03-0.05 ppm

PS: do not confuse these actual ELEMENTAL ppm with any measurements
or conversion rates of any instrument or "TDS meter", as what ever it may display, it will not correspond to these. Hence do not make any total nor deduce a nutrient concentration in "ppm", or anything even remotely related from them. These specs are based on actual ppm of nutrient formulas composed by components. You need to use proper calculation formulas and methods, known from nutrient making to make any sense of them in terms of total concentration.

The symptoms showing only with older and mature leafs draws the deficiency down to the mobile elements.

Nitrogen
Phosphorus
Potassium
Magnesium
Sulfur

As nitrogen and phosphorus can rather be eliminated,
we have 3 left: Potassium - Magnesium - Sulfur

If you spray with Epsom Salts (as recommended by urbangardenfarmer), you will supplement with both Mg and S. But I would also insure that your nutrients have enough Potassium content, as it becomes even more vital with flowering.

Nutrient specs for tomato may vary with varieties, climate and growing rates as well. Some variety may be thriving (blooming and fruiting) with some "standard nutrient formula", while others may require (much) more Potassium in relation to the Nitrogen content.

The funny (but actually plausible) thing here is, that the better and quicker your tomato grow, the more demanding they get about optimal nutrition. Except some "Dutch greenhouse varieties" that produce high yield with a more standardized (and cheap) nitrogen focussed formula. Well, as we know those are RED, perfectly calibrated, early, high yielded - but taste like water ;-)

Here is a typical tomato formula that may still vary with type and climate, but gives you a good idea of actual elemental requirements:

N- 150-170 ppm
P- 35-50 ppm
K - 200-250 (280) ppm
Ca - 150 ppm
Mg- 45-50 ppm
S - 55-90 ppm
Fe- 2.8 ppm
Cu- 0.2-0.25 ppm
Mn -0.8 ppm
Zn -0.3 ppm
B- 0.7 ppm
Mo -0.03-0.05 ppm

PS: do not confuse these actual ELEMENTAL ppm with any measurements
or conversion rates of any instrument or "TDS meter", as what ever it may display, it will not correspond to these. Hence do not make any total nor deduce a nutrient concentration in "ppm", or anything even remotely related from them. These specs are based on actual ppm of nutrient formulas composed by components. You need to use proper calculation formulas and methods, known from nutrient making to make any sense of them in terms of total concentration.

@trenhes, you want to spray every 10 days or so. You also want to do all foliar feeding right before your lights come on. That way you don't have to worry about leaf burn and/or fungus, mold problems.