Seedling's white edges

Okay, so I have those 3 white widows and 3 northern lights, they are about 7 days old. Temperature is between 74-85 F and they currently under two 65w cfls with two 25w from the sides. PH is about 7, no nutes right now. light cycle: 18/6.

All of them looks perfectly Healthy but yesterday I've noticesd one of the widows strat getting those white shriveling edges, also noticed that the stem is a bit redish than the others.
I realy Have no idea What it could be, thought its a light burn at first, but it kept growing even though I moved the plant.



Also added one of my healthy widows.

Heat stress from the lights being too close and no fan to circulate the heat maybe/possibly/probably. Forget about pH completly and they dont need ferts this young or for a while.

Purple stem could be stress from heat too/most likely. Hope this helps Peace

Thanks Kingrow1, already have a fan delivering cool breeze, but just incase moved them a little bit more from the lights/

85 degrees is a bit too high. also red stems could be nitrogen/phosphorus deficiency a 50/50 split between the 2, seeing as how young they are, id guess a lil of both, they need N for the growth, and P for the rooting.