It could be a couple things. Nutrient burn, Nutrients lockout, light burn. First thing I would do is lower light level to help her recover. Water to run off check my ec and ph of run off if out range correct them. Lower next feed till you see she recovers. Then slowly ramp everything back up. Also make sure your not letting pots dry out to much. To dry can cause ec to up then ph drop cause of the concentrated salts with no water.