No nutrients, using bottled water, sometimes RO bottled water, no superthrive or cal-mag

I guess it could be heat stress, the floros are about 6" away.. but the other one that is the same size looks perfectly fine. Sorry about the blurry picture.

So i put the cubes in my system, flood the pots half way.. then eventually the roots will grow down to the part that will reach the water? that means there will be like 6" of space that will never have water (which means those roots will never have water in those 6") below the rockwool right? which would mean i should water the rockwool by hand every few days, even when its in the system?

or what do you mean by watering every six hours once its in my system? the rockwool? sorry for being so slow hah..