Rx 590 heat damage??

Let me start this off by saying i am relatively new to the pc gaming world. My current build is a RX 590, Ryzen 5 2600, 600 W psu, and a B450M pro-VDH plus motherboard.

Up until about 3 days ago, I have had no issues whatsoever and have had great FPS on any game i played. I have had the pc for about 8 or so months now. One night, after probably 8 hours of gaming i noticed significant fps drops. I randomly went from 60-90 fps to a 30-60 fps range. This all seemed to happen in one night. I kind of figured it was an issue with the game, not my hardware.. Fast forward to now, about 3 days later my frames are still on average 20-30 fps lower than what they used to be. I have compared fps in r6 siege , rust, and tarkov with my friend having the EXACT (we built them together) same build and he is getting dramatically better frames than I am. He seems to get 20+ more frames than i do in all situations. After this realization, we benchmarked using novabench and my gpu scored 597 while his was in the high 900's. Compared to other user benchmarks of the rx 590, my score is 40% lower. Being a noob, i realised that for the past 8ish months i have been running my gpu in the high 70's to low 80s Celsius(i thought these were normal temps somehow). Assuming pretty heavy usage over the last 8 months, would these temps be enough to perminatley damage an RX 590? Do i need to buy a new graphics card? I should also mention my friend has been gaming with his side pannel off for the past 4 months and does not game as much as i do. I guess i just dont know how else to tell if my gpu is damaged and dont know if i should be buying a new gpu or not. Any guidance would be greatly appreciated. If more clarification is needed please let me know.