Yellow leaves plz help

Hello all like it says i have some clones i just put into my new hydro flood and drain table and there a little yellow. i am lost as to what it might be i use supernatural aqua grow so the nitro should not be a problem my room is sitting at a temp between 75-80 depending on the time of day. the only thing i can think of is salt build up but then again they have only been in there for about 2 weeks. so those are my conclusins please help me this problem i now its early so i want to catch it before it gets any worse. thanks and i await ur replies.

Most clones at a early age have a little yellowing just keep the feed going in and the clones will out grow this problem.Check how much you are feeding too if the clones have roots showing through the cubes up the feed to full.If the clone dont have roots showing yet but have took hold then just feed harf strenth nutrients.If the yellowing continues has the plants get older i would put them on water no nutrients ph of 5.5 for a few days to flush any salt build up's that you may have.