its not a ph, watering or nute burn problem. When growing in Rock wool you must add a calcium suplement b/c it severly lacks any in the medium. A good product is Calmag, just do 5ml every watering. Otherwise, you can use epsom salt at 1/2 - 1 tbls per gallon. One of these things should clear the problem right up and turn those little girls green again.
BUMP bUMP yeah maybe could b needing sum CalMag, and yea its agood product, however....... CAL and MAG difficiencies i dont believe reveal themselves in this manner??? cal mag deffs show up as rust looking spots on the leaves, yes? depending on how big the spots, willdepend on how big the difficiancy??? yes? could b overwatering but the leaves would exhibit leaf curl to help dissapate the excess water which its not???
Still say NUTE BURN WAY TOO EARLY 4 NUTES!... but ur gonna still have to make a choice???? based upon all this info ( misinfo?) ...... so I wish u good luck and success! research the subjucts, nute burn, overwatering, ph issues, and use ALL info provided and make an educated dicission??
FYI as a scape goat it still is poss even with that gr8 equip u have that it could b a PH issue???? u really dont need a meter if ur using soil as it is very forgiving???? however hydro? that rockwool will expose every weekness! u may have? cuz the plant soaks up every mistake when using hydro! i hate that too! dont act to hasty though... if u can get a meter and stay off the nutes, i would even flush the girls with some RO or distilled water . NONTHELESS these r ur girls and i dont pretend to know more abouth them than u? So use the FORCE LUKE! and Happy Growing!