Too seperate root systems in one tub?? I can't remember if I read about this before or I just thought of it, but you might try blocking out each side of the net pots that are closest to each other with some soart of plastic so it creats a kind of barior so the roots don't go out that particular side of the pots towards the other net pot. Maybe it could help. Will try to think of some other possibilities. Also if you are not veging to long you may not have a real problem.
Adieu