My early 2011 2.2 quad-i7 high res AG MBP is starting to show discoloration to the bottom of the screen. On a black background it appears as a 1" lighter strip across the bottom. On a blue or white background, it's orange. Seems to be worse on the bottom right corner. Doesn't appear to go away when the machine has been powered off. I'm out of warranty at this point, so I'll probably have to hit up my Amex extended warranty. Is this common? Apple defect due to heat?