Young one turning brownish/purple?

So this plant had a ph issue early on. But that was taken care of before this problem started to arise. It started on the 29th with a blueish/purple hue on the largest leaf. I though it was because of temps getting to 70 when lights were off. This has been correct for 3 days now and the color change seems to be spreading.

Looks more like a brown now with a dash of purple starting a bit more in from this main section. Also the tips turned white-ish early yesterday, so I thought it might be light bleaching, so ive moved my LED's to 31" and it seems to be spreading still.

On the 30th I added about 10% of cal/mag that was 1-1-2 NPK since these were in coco. So I dont think its a nute burn, but maybe ive cause some sort of lockout on this one. 2 other plants that are smaller dont have this going on at all. They are healthy. What do ya think?

So the discoloration has stopped but you can see its gotten worse on the affected parts. I flushed yesterday and fed 1/4 nutes 3-1-3. Still not exactly sure what the issue was. These are in coco and 2 other plants which have been fed the same showed no signs. Any ideas?

you fed nutes to a seedling........that kills them. sorry

it's toast you nuked it.

lol...or maybe he accidently left a blow dryer next to it?