bright yellow blotches, looks like heat burn but i think it's not

so this is brand new... i had some yellow blotches from heat before but it doesn't look like it... plus it's on the same plant in my scrog, and it just appeared today after the feeding yesterday.

details: coco-perlite 50-50. week 8 in flowering. hindu kush. flushed frequently. last night's feeding: total EC 1500: 1150 of HESI coco (8-6-10 + micro), + 350 of HESI pk13/14 + 1 tbsp blackstrap molasses per gallon, 5ml/l enzymes.

the blotches appear mostly where there is strong light, but also in some shaded leaves. my scrog is very messy so branches from the same plant are everywhere, and in neighboring branches I don't see the blotches, so i'm pretty sure (but not a 100%) that this has something to do with the feeding yesterday. But then, aside from the pk dosage being a little higher this time (i've used it before @200EC, but not in the previous feeding), it was pretty much a regular. so i'm suspecting the pk is the culprit. I've read it should be used with caution, but I figured I would just be tipping the scale a bit for more pk than N, in such an advanced stage of flowering. guess I was wrong and what I had was enough.

So I'm already on my way to flushing the hell out of it, but I would like your opinion on what I did wrong, so I won't do it again.

(note that all units are microsiemens, to get actual EC units devide by 1000, to get ppm multiply by 0.5-0.7).

yeah, i guess i should have titled it: 'extreme plant death one hour after alien hijack' i might have gotten some more responses

come on people, this is serious stuff here!

i flushed the plant down from run off of more than 2000microS to 1000, hoping this will help, see tonight if it doesnt get worst I'll try to put it on 1500. I wonder if I should treat the coco like water in terms of EC. The thing is, I'm not sure if runoff is telling me the truth about the medium EC. For instance when I take a sample from the top of the medium where the roots are, the EC can be very low (300-700). But then @ runoff I get much more. So I wonder who's telling the truth, and what is the truth. Should I treat it like water somehow and pretend to know the amounts and/or (??) concentration of salts in my medium, and try to figure out if the plant is taking them in properly (for instance how do salt buildups occur? what do they mean? Are they measured by medium EC?)? or more like soil and just hope for the best on it, with an occasional flush?

My pH seems to be at very good value both at sample and runoff, around 5.8 up and down.