yellowing edges on clones

Ok im freakin out cuz some of my litle babbie girls are startin to yellow at the eges then curl up and start to shrival. I have pics below. Thies litle girls are clones and have been veging for about 2 weeks. I am using 26w cfls in a custum built hood. I have 6 runing curently.I am growing in miricalgro potting soil my temps stay around 70-80 and my humidty is about 40%. I have fed only half of them the other half has been strait water and still all have the same problem. So i think that rules out nut burn. My ph is aroun6.2-6.5 between the 7 plants. any help would be greatly appreciated and any advice on moving away from mircal grow to somthin better would be nice to thanks and i hpe evryone can see the pics clearly

get them out of the miracle gro. it works for some people but not all.

if im not mistaken doesnt all miracle gro soil have nutes in it?

Yes I Def Agree To Get Them Out Of Miraclegro But I Dont Think That Is The Problem The Mother Is In It And Is Doing Fine And I Have Had A Few Other Grows Of The Same W/w Strain With It Without This Problem.miriclegro Is Just Convient For Me.