Way Way way too much nitrogen...Severe lockout is what you have here I am almost sure...When you switch to flower any built up nitrogen will make the plant go crazy cakes...Happened to me a lot, perhaps not that badly, but my leaves always curled under, on plants that were sensitive to nutes...a plant that likes nutes won't usually have this issue...flush and then water with some sugar water...sounds weird but you would be surprised...the burnt looking leaves and what not won't recover....Here is what I would do...Go ahead and take that plant out of it's pot and give it some new soil, then water with some sugar water of the right Ph, just a little...that way you cna check out your roots and make sure there isn't any root rot or anything going on under there...If you choose to just flush you are going to have to use a whole lot of water...a whole lot! Or it won't be enough and it will just get worse..., also if it is an issue with your roots, flushing would also make the issue worse...I am fairly sure it is nute burn, but repotting would allow you to check the roots as well as removing the extra nutes...and you would be starting again with fresh prenuted soil
