What up man... first off you need to get you some PH Up and PH Down from your local hydro store or offline. My friend tries using a bunch of odd shit for his ferts and ph adjustments and he royally fucked up his plants. If you know what your doing, it may work well but for how important your PH is, purchasing good liquid PH Up and Down for hydro is def. worth your while.
That damn Rockwool is a bitch aint it? You just need to keep all the light from your wool and you will not have that problem. If you got some plastic laying around, tin, aluminum foil.. anything to cover the top of your net pots/hydroton you shouldn't have to worry about that mold too much. Personally I have had wool mold up on me too easy and after seeing it stunt growth by about two weeks.. I decided RW wasn't for me. I just stick the clone straight to the bottom of the netpot and fill it up with hydroton. The bubble mists the bottom and it seems to root in about a week. I pop seeds in Rockwool, let them grow from the rockwool until they are about 2" tall including the root and just move straight over to netpot/hydroton. They seem to root and take off a little quicker that way.
If you want or have to keep using the Rockwool, I would toss the moldy one and use a fresh one. Also wipe off and spray your netpot or anything that mold was around/in contact with Lysol or something to disinfect. Keep your plant clear obviously.