Hello, my 2011 MBP recently started having what looks like a grey smudge mark on the screen. It is about an inch and a half wide and only shows up when the screen is displaying dark colors. Any ideas as to what this is? I've had the computer since May and this just started like yesterday (or I first noticed it then at least.) Should I take my MBP into an Apple Store? Here is a picture of it (taken with my iphone) though it doesn't really do it justice. Any thoughts?