Probably because you've been feeding them and they're burned. They don't need it yet.

You flush the plant by watering twice/three time the volume of the pot with ph balanced water.

Like LIP said and I told you in the other post, this is basic, basic stuff and is readily available. Read my entire grow log so far, I'm a month ahead of you and I'm going ok so far. You can see what I've been doing, a lot of the basic topics are covered in that thread too. Good luck.