I have the same problem and it keeps getting worse. Two weeks ago the issue happened at around 78°C now it's already happening at 69°C. I've send my card into RMA today.
There was another thread in which the issue was solved by putting the card into another PCIe slot, which might be worth trying. I don't have a replacement card so I'm concerned to send it to RMA because it will take quite some time until I receive ...
I have exactly the same card and got the same problem. Once my card reaches 76 degrees the fans go up to 100%. Afterburner or the Asus GPU Tweak still show that the fan is running at a low percentage but from the reported fan rpm the fans are running...