QT tank start up ?s

The top of my DT is rocking back and forth as far as agitation. I do have a canopy but there's two fans circulating plenty of air. At night my water is at 79 degrees in the day it does hit 80

 

Well I woke up last night at about 2 to find my tank temp at 82.1 degrees.

My heater wasn't on(so I thought) so I started messing with all my equipment to figure out what was producing so much heat. Turnned my fuge light off, turnned pumps off(should have started with my heater) nothing. Decided to turn my canopy fans on and it dropped to 80 which is my daytime temps with the lights on. My heater was set to 78 and this is where I laugh at myself... But the light inside of it didn't turn on so I never figured that was it but decided to turn the temp down on it. I think 68 was as low as it it goes and nothing. Unplugged it and the temp started dropping I'm not sure if 82 is enough to kill my fish but I know it defiantly stressed them out.

 

Well my main lights have been on for over an hour and I still have not gone above 79.4 degrees. Seems as if I stressed them out with heat. :/

Is 82 enough to kill? Any thoughts on whether I should still QT the 4 fish I still have. Even without the use of copper?

 

Well I guess at this point ill do nothing. If they live they live~ I'm tired of stressing over it

 

I don't think 82 would kill your fish. At this point, you really have done and checked EVERYTHING I can possibly think of. It makes absolutely no sense that your fish kept dying. Just for the heck of it, if you decide to add any more fish at some point, I would get them from a different store, just an experiment.

 

Bad food?