I just tested water parameters and all checked out fine. I would almost count water quality out, as the issue has been happening for as long as i can remember.
Params :
Calcium - 450
Magnesium - 1350
Alkalinity - 9.6
Nitrates and Phosphates are undetectable.
Water changes are done 30% weekly with natural, ozone injected, sea water.
I think it is a parasite, just not sure what it could be other than copepods.