Seedlings Growing, but edges are yellow/brittle? *PHOTOS* (Around 6 weeks old)

My seedlings (6 weeks old according to the guy I got them from) are growing, but I think they are stunted in growth. I had them for two weeks before I began to see any new growth, and in the second week I had them, I nute burned a few.

People here told me to toss them and start over, but I don't have money for new ones right now so I just left them under the lights, then they started growing.

Is the yellow on them from the nute burn, or does it mean they need nutes?

Also some of the new growth is dark green and a bit rounded, they don't look normal. What is wrong with them?

They are in a 4x2 Sun Hut with a 400W MH 16/8, in fox farms soil. After I nute burned them I did flush the soil with PH'd water.

I don't have duct fans yet so I keep it unzipped with a regular fan blowing in there to disperse the heat (without fan it gets up to 85, with fan it hovers around 76-80.)

Looks like you stressed them when you gave them nutes...should have waited a bit on that. Might have some root damage, try just giving them water for awhile and you can even add a bit of hydrogen peroxide to help your plants root system develop. I've found it pretty beneficial when I have start my seeds. Your heat also isnt too much of a problem, your seedlings need a good amount of humidity (moisture) to thrive.