On one of the smaller plants I see some spotting that looks like it could be magnesium deficiency. If these spotts are a yellow color, chances are you need some mg in there. No offense but if I were in your shoes, I'd go back to soil growing. It's easier. Using the method you are is complicated and you really have to know what you're doing to make it work. Chances are you've spent a chunk of money on this setup and I know how disappointing it is to see your plants have these problems. Soil really is easiest for most people. Again, no offense, just my opinion.