No rockwool is nessacery it will grow just fine with out it. Sound like your plant is stressed just leave it alone and give it time to heal good luck....
The 400w hps is going to overshadow the rest of the light. I would say just use the 400w the rest of the light is added heat. well you mite be able to use the 150w with the 400w too good luck....
well try H2O2 a half cup every three or four days it will fix that rite up. I been useing for 4 almost 5 years works great my roots are nice and white good luck..
Try lowering the light. the closer the light the bigger the buds. I haves a 1000w HPS and i keep it 12in from the top buds but you'll need pleanty of air movement so not to burn the tops and i get a Qter p per plant. Good luck.......