81.5 is fine as long as it isn’t spiking up and down. Stability is everything, many antidotal experiance s are that SPS actually grow much faster at that temp. What are you doing for makeup water, Fans really increase evaporation and if you are dumping a gallon or two of RODI in the tank every few days, that’s going to shock the shit out of everything.
I had a similar issue a few years ago, finally decided the only recent change was a new bucket of the same brand of salt. I switched to a new bucket, did a water change and everything was fine the next day. Fish were fine, corals just shriveled up.
I've had issues with temp swings in the summer. Keeping the tank stable is the best chance of success. I invested in a Chiller and do bi weekly water changes. That seemed to work. Are you looking into a chiller?