Not sure what it is but I think it’s nute Burn

hey guys I’m having some trouble with my grow I’m not sure what it is but I think it’s nutrient burn but I’m not sure what’s it’s getting to much of or too little or how to fix it. It’s under 2 100w full spectrum led lights in dwc and I’m using canna aqua Vega for nutes and the foam like thing it’s growing in was white and now it’s kinda green is that normal or could it be mild or something. It stretched like fuck as a seedling which is why it’s bent over it’s on 18/6 lights
 

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OR,,,,Simply cover the pot by making a hole in the center of a piece of something that light can't get through and cutting a line to it.
Now twist the thing to put it around the stem and set it on top of the pot.
No light on the pot surface/NO algae
Ah yeah I’ll use cardboard or something. Should I treat it first or will stopping the light kill it off
 
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