I flush the rockwool let it soak in distilled ph 6.0 water for 24 hours put the seedlings in after they have popped. I try to be sanitary at possible clean eveything wear gloves. I gave them some flora duo gro about 2ml, a little resclear to protect against fungi and 2ml of calmag in a gallon of ph 6.0 distilled water. Im thinking too much nitrogen or maybe over watered. I also had my light a little to close, so i moved it up a few inches. I attached a couple of photos the 2 big cubes are what I hope to grow. The other is just a bag weed.