Also check out capacitors and voltage regulators on mainboard.
Good tip as the OP's motherboard is a fair few years old some capacitors could be bulging (mostly on top) or even leaking at this stage.
Quick and easy to check, just shutdown the rig, unplug the power and open the case and inspect the motherboard.
Some capacitors could be blocked by the heatsink and might be hard to see.
Should have added I already pulled the 750ti and it was still happening.
Check the motherboard for leaking/bulging capacitors. If that's all good maybe try and replace the PSU with another one (other pc, a friends ...)
It always helps if you research hardware before you buy it.
Hardwaresecrets could have just been unlucky with that PSU and yours may not have the same problem. It's hard to tell.
Replace the PSU with another one (don't go buy a new one until you're 1000% sure your PSU is the problem) and see how you go.
Could even be an OS or driver issue .. who knows.
I have it in a home made wind tunnel (big box with box fans at either end, not just for cooling it also helps keep my cat out) gpu never get's above 65c
Check CPU temp too btw, just to be sure. Altho it sounds like your wind tunnel is providing some good cooling.
, and the start of hustling up a new cheapo rig. 
(big box with box fans at either end, not just for cooling it also helps keep my cat out) gpu never get's above 65c