Whats is wrong with my plant? Coco

It's roughly 2-3 weeks old from seed in coco. Ph water/nutes to 5.8 gave it a little bit of cal/mag and olivias clone solution a week ago. Under a 250w hps air cooled about 4-5" away. I can touch the tube and not feel heat at all so I dont think it can be heat. Anyone know what the problem is? Thanks


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Either a nute burn or a phosphorus def, 5.8 is a little low for soil but this doesn't look like a lockout because nitrogen gets locked out first and I don't see a nitrogen def.

I havent gave them any nutes though.. Just a little cal/mag like a very small amount. the top leaves are turning a bit lighter green too, which is kind of hard to see in the pic.