Nitrogen if anything for adding nutes, but you really should test the pH of your runoff water before you do that. If it's outside the 6-6.5 range, you should alter it to match that, and it'll fee up some of the nutes that you've already got in there. The other reason for yellowing is that it's not getting light to them, and if that's the case you might want to try tying it down to expose those ones to more light. Good luck! Oh, and you can defintely switch to 12/12 now.
UnitedParcelSecrets Reviewed by UnitedParcelSecrets on . 10 weeks in veg?? I have 14 plants in 3 gal. pots, MH and HPS lighting (plenty!), room temp averages 75 - 78 degrees, humidity averages about 55-60%, feeding some nutes higher in N every 4 days with plain water every other feeding (2 days). Plants are now in week 13. They started out VERY spindly and it was recommended by several respondants that I toss the lot of them and start over, but I couldn't bring myself to do it! 8 of them are White Widow, rest are bag seeds. Plants now average about 3' tall, some Rating: 5