You just need to get your timing right when feeding your plants. Like if you're running HIDs water 2-3 times a day. CFLs 2 times. 1 water in the morning and another watering 1 hour before lights go off. And if it gets really hot in the room you may need to water more often.

with straight rockwool you gonna run into a lot of problems like this, you could use pots filled with hydroton to give the roots some breathing room.