NVIDIA cards start throttling at around 80c, do you have good airflow in your case? try cleaning up your wires so they are not hindering the airflow, also maybe install some more case fans.
Before you spend money though, open the side of your case and put a normal fan next the tower blowing at your GPU, see if that helps bring the temps down, and improves the performance at all. Clean out any dust in the case as well.