Although not normal not impossible either. You could always replace it with another. For newegg all it takes is the cost of return shipping.
You should also be able to run the GPU overclocked without increasing voltage.
One other possible problem is that your PSU is running off of two PCI-E adapters. Which are by no means ideal (could be a source of the problem, but I wouldn't look into replacing it unless you can switch your PSU with a 750w, or higher of a good brand, just temporarily to test, say another PSU a friend may have).
Nope... None of those. Ended up being a glitch specific to MSI Afterburner. Sapphire Trixx works perfectly...
Matched them up no problem. Almost killed the second card by accident though. LOL!