Looks similar to Malathion burn. The only other thing I've found that is even remotely similar is Molybdenum deficiency.

From some reading, I'm thinking it might be Molybdenum deficiency. 100% sure it's not Malathion burn. Would you know whether extra fertilizer that has trace amounts of Molybdenum would fix it?

Molybdenum deficiency seems to occur in soils that are acidic. This is probably a ph problem, but can also be caused by high levels of sulfate. Peat can be acidic too, so if you have that in your soil naturally, it could cause the problem.

Most soils contain sufficient quantities of molybdenum, but if the soil is too acidic it won't be as available to your plants. See link below.

You may need to raise the soil ph so that it's more alkaline. Is there some place near you where you can get your soil tested for ph? I would do that if possible, as they can normally tell you more precisely how to remedy the situation.

Without knowing your soil's ph it's hard to tell how much lime, for example, you should add to correct the situation.

This should be a fairly easy fix once you know how acidic your soil is. Of course, you can always experiment by adding lime yourself which, if you do it conservatively, following package directions, could help. You wouldn't want to go too much the other way and end up with soil that's too alkaline, so don't start out going too crazy with the garden lime. :-)

Best of luck!

Here is a link that might be useful: Soil and Applied Molybdenum

Just as you suspected -- they just weren't hardened off -- environmental stress.

If they weren't hardened off properly any new leaves that have grown in the last 4 weeks should be fine and it wouldn't be creeping up to newer leaves. I fertilize every month with a general fert(10-10-10, 14-14-14) with all the micros and foliar feed every week with 1/4 strength. If your PH is between 5.5 and 7 then the PH is not the cause for the deficiency. JMO for those followers that enjoy discrediting my every post.

I did a pH test with some home kit and it came out in the 5 range (not really precise) so I'm going to take a lucky guess that there is a deficiency problem.

My new question is, what can I do about it? Various articles I've read have suggested that one shouldn't add lime during the growing season as it mixes poorly with fertilizer. Thanks again!

Find a general purpose fertilizer(10-10-10 or 14-14-14) with Molybdenum in it that mixes with water for faster delivery and follow the directions. If you want to get your PH up, water in a couple Tbsp of baking soda the next time you water. Repeat until you get it where you want it. Don't try to change it too fast or you'll end up with more problems.

Sounds awesome. I'm taking a go at it. Thanks.

I thought I'd share a pic of a how our tomato leaves look (and the corn, squash, petunias, etc.) after the last couple hail storms. The hail stones were small - say pea-size or so - and the leaves didn't scar up until a couple days later. Does the damage seem similar (the white areas, that is) to the damage you saw?

I can't say they looked like that what so ever. Giving them some extra fertilizer that had Molybdenum and watering with some baking soda in, the whitening of my leaves has stopped on about 75% of my tomatoes and the spread on the rest of them has drastically slowed down. Success!