Just so I don't have to read back over everything you wrote, are you giving them anything to eat? They should have no nutrients at this point. The only thing you should be giving them at this point is a little B1, preferably SuperThrive, to help with shock and root development. Those pictures are blurry, but it looks like a nutrient problem, probably some kind of burn. You get burns when you feed too much. Also perhaps it is heat stress. How close are your lights? Should be at least a foot back at this point with fluoros, and gradually move closer over about 2 or 3 weeks.

Watering every 6 hours is just a guess for your setup, and it refers to when everything is set up and going, not now. A few times per day you should flood your net pots about half way up, but don't flood the rockwool. It will stay plenty wet on it's own.

Keep PH of everything about 5.5.