pH seems like an issue, or it could be salt build up. If you know how osmosis works it's easier to understand. If the salt content becomes too high, its difficult for the plants to take up anything including water. If you over fertilized you probably threw the pH off as well. I assume nutes were synthetic?
I always go 3/4 strength and with many strains I don't know I feed until the very tips burn, then just water for 2 waterings, and back at it with 1/2 strength. Once you know your plant you will know it's threshold.
I have never grown the holy grail, but I would flush it with fresh water wait a few days and cut it. If you got nothing then Freeze it immediately and make some ice wax