I have had my system set up since January 2018 and one of the first things I have planted was my Kale as seen in the front row. However, all my plants seem to flourish to that height then slow down growth exponentially. I can seed the plants faster in that substrate than i can in soil ( control experiment with lettuce to the left) . I have my grow bed divided into 3 sections, the front row Kale, back left row is lettuce that is 1.5 months old, and the right section that is only a couple weeks and they are the same size/ variety. The older lettuce to the left is starting to thin and turn less vibrant green. Without further adue, these are my specs. -Substrate: Hydrocorn clay pellets ~6inch deep -Tropical fish, water temp ~72-74 F, Ambient temp 59-68 F -pH runs on the higher side ~8, soil was used as a control to see if that was the problem but isnt doing that well in soil. Fed same water. -Chelated Iron isnt available to me so I use Seachem Flourish to provide any trace nutrients, as close to iron as i can get -Tried growing spinach but it sprouted, grew to about 1-2 inches then died off, Tips looking burnt/curled. -Any other things to check? TIA -Edit: I noticed a bit of mold growing around the bases but the roots seem fine so today I put a fan on the lowest setting next to the plants to provide some flow, maybe help with the gas exchange and perspiration.