Do not water the rockwool. Just increase the level of water in the bucket until it soaks about half the net pot, not the rockwool. This is assuming that you put the girls in when the roots reach at least half way down the inside of the pot, so they will get wet during flooding. This needs to happen. Make it so. Once you see roots start to come out of the rockwool, or the girls are looking nice and healthy, that's the time to put them in hydroton and start feeding at 1/4 strength. The roots in air will get what they need through the few inches of water covering the bottom of them, and when you flood them. Roots need oxygen. As much as possible. Obviously if you plan on having the bottom of the roots in solution as I suggested, you will need to have some way of varying the solution level. If not, flood more frequently.

I don't know what to tell you about big bertha. If the light is 6" back it's probably not heat stress, but some chemical thing. I do know that when plants are chemically stressed, they can't take as much light. Perhaps you should check the problem charts I and others have posted. Sorry I can't be more help.