After just going a round with Gravity. I would say that's it, the gravity. It will burn your plants up starting with the large leaves.

Did you use it full strenght like the bottle says ? And raise your light way up, between the 2, light and gravity it burns.

I would drain rez and put back nutes. If they look like that it's done, much more and you will not get much out of them. Flush the last week.

They will thicken up good but don't let the gravity go any farther.