Yeah, lots of potentially issues that could cause that. Water quality, lights, chemical parameters out of whack. I would put stray voltage probably somewhere between "Corals dying of old age" and "Someone put a voodoo curse on you" as far as potential causes though.
I mean if you do have some open electricity getting into the tank and you know this then I would definitely address that issue.
And if your impeller is cracked, might want to replace the pump/impeller just because you can.