Are you having high temperatures? What media are the Roma's in. clay pebbles, or what? DO you have any other plants growing sucessfully in your current nute mix? For active growing tomato plants your E&F schedule seems not enough;

Well I think I have found the problem, key word being, "think."

My nutes start out at 5.2-5.5 and after a week they go to 6.7-6.8. So I might be suffering multiple nute lockout due to high ph.

Temps are around 28C and they are in clay pebbles. They grew well before and normally do well after weekly water changes. I'll start staying on top of my nute ph daily now.

What would you suggest for a proper E&F schedule?

Thanks,
Okami

I too have had high pH problems, but I've just discovered "pH Down" from General Hydroponics; it works very well, and seems to be highly buffered (pH changes tend to last);

Well, it doesn't look like the weather is too hot there; hmmmn

Maybe:

You diluted your nute mix so your last nute mix wasn't too strong...
Salt build-up in the clay pebbles?

Since you suspect overwatering this might seem counter-intuitive, but if the leaves are a bit limp I'd increase the frequency of the E&F; four hours with the roots exposed to the air sounds too long, but it sounds like you've had success with this before, so this is puzzling;

I've grown tomatoes in an E&F system using clay pebbles for two years, and my schedule is six minutes off, 2-3 minutes on; however, I've got 2 litre bottle systems, which makes it easy to cycle quickly:

It sounds like you're using a table type E&F which would make it difficult to cycle that quickly.

Maybe try leeching out the built up salts in the pebbles, other than that I'm perplexed.

Ph Down would be a godsend, but check where I'm at. Literally everything is DIY. The set up, wiring, lights, chemical nutrients was all made or wired up by me. I spent 2 months just researching how to do it and finding the materials. My Ph down currently consists of 85% phophoric acid diluted with water(always add acid to water, never water to acid). My Ph up consists of potassium hydroxide.

I'll probably start a once every 3 week flushing and up the E&F cycles. I can go with a every 3 hour for 15 minutes on. I'll be checking the Ph daily though as I think if I got this under control everything else might follow. I'm not dealing with limp leaves, but with leaves that curl under themselves like a ram's horn.

Nice set up. I see you used that one online page's set up. I wish I had it so easy. I'm planning on adding a salad mix set up in the winter and actually getting flat land for a greenhouse in late winter/early spring.

Okami

Yes, I tried the online style design; low cost to build, easy to clean, very easy to move; I've had good luck with it, although I just cannot find a big enough container that I can eaily connect to the PVC pipe that will hold most tomato rootballs! I'm going with a modified drip system for the 'maters.

I did find a reference to sulphur deficiency causing downward leaf curl, maybe try adding small amounts of sulphur?

Anyway, good luck,
Ted