Maybe get a fan to help cool the tank when the lights are on. My tanks are near windows in a basement suite & I once hit 86F before I started using fans. Then it maxed at 81F. Its not frying the fish but the fact that higher water temp reduces dissolved oxygen content in the water & sw already holds less oxygen than fw so in the heat of summer, the risk is suffocating the fish
I usually jack up the flow & add an air pump when it really heats up. I also change my photoperiod so the lights are off in the hottest period of the day & on later at night after it cools off.
Anthony