It doesn't look like the gpu is the problem... the cpu LOOKS to be more likely.
The turbo clock average was 2.6ghz. According to notebookcheck:
"Each core offers a base speed of 2.5GHz but can dynamically increase clock rates with Turbo Boost up to 3.3GHz (for 4 active cores), 3.4GHz (for 2 active cores) and 3.5GHz (for 1 active core)."
That it didn't nail 3.3ghz average leads me to believe that it's either:
-thermal throttling, though you said it was fine.... but 80C on a laptop gpu isn't unusual for them either.
-power throttling. Laptops do have more stringent power limits implemented, but that shouldn't suddenly change one day and start doing worse, thus leading it on to thermals... but then I'm going in circles.
-recent Windows Update broke your settings, and you need to reinstall all the drivers again. This happens sometimes. Windows is dumb.