Just use the flashlight, and point it to hdmi conectors and look if the cooler has gone bad. Just like i sad i have sapphire, xfx, and powercolor cards an on 4 out of 12 coolers are melted. When this happens somethimes it hashes less, somethimes it crashes rig. If you put your hand over the card it looks cooler then the rest because ic cooles with half or less cooler that is still soldered to copper base. So air seems cooler but when you look in software card hashes less and trotles.
Good luck