Gorilla Girl XL Auto

Yep, it's either nute burn from to much P or K, or it's a Cal/Mag deficiency just starting. Check ppms of runoff. If they're good then add some calmag to the next feed and it should stop the spread. It's also vaguely possible that those leaves are being cannibalized by the plant if they aren't getting any light, but that seems least likely to me. Good luck!