90C will cause shutdown or frame rate to drop. Maybe just tun up the fan in the radeon software?
The card experiencing those kinds of temps regularly for a few years could possibly affect the thermal paste. or the card may need a cleaning. I would check those things if the fan speed increase does not help. I have a 570 nitro and the temps never reach 70 while gaming. I know the blower is a bad setup but 20c hotter on a slower version version of the card isn't normal.