Tomato Lower Leaves Yellowing

[GpsFrontier]

OK, it would still be much better if I could see the setup and plants, rather than trying to guess. Pictures can show issues you wouldn't even think to ask. Here are my first thoughts on the reply's to the questions I asked:

1. Glad the roots look white and healthy, but in 3 weeks I would expect much more growth of the foliage.
2. Water temp is a slightly low at 65F, but nothing significant. But if it's much lower, low temps inhibit plant growth.
3. This is a little low (77 F day, and 50 F night) but isn't bad. Just could be a little warmer, but I expect temps will rise shortly.
4. I am not familiar with these nutrients. Do you have a link to them so I can see what they are?
5. I still don't know how much your using, and/or if your fallowing manufactures directions.
6. That's a fairly good amount of sunlight, But if both are growing slowly, temperature may be playing a role. However I still cant see the system or plants, as well as don't know anything about the nutrients and how your mixing them.
7. This could be a potential problem. What chemical and mineral elements does that 220ppm consist of? What amount of ppm's of each chemical and mineral is in the water? In other words there is 220 ppm's but of what?
8. pH is not bad, but I would lower it slightly to about 6.0. Does the pH fluctuate much?