600 watt light six feet up in the air gives you 100 Watts of light at the floor which is more than the tiny plants need at this point. So if you have it 4 feet up then they are getting 200 Watts, and btw too much light will show up as a Mag. Deficient (purple stems and yellowing leafs that fold downward trying to hide from the light.
Another thing is the over watering, and over feeding, I'm wondering why you decided to water and feed every day and water with out nutes on the 7th day. As mentioned before if you are in the right size pot you only need to water w/o nutes once per week by then the pot should be nice and light when you lift it to feel how heavy it is.
And feeding nutes is only required once the plant has filled the pot with roots so the plant can eat all the plant food in that O.F. soil which typically last two months when vegging small plants and repotting as needed into new soil.
So now just stop over watering, stop over feeding and stop giving them too much light.