My MBP casing has random blemishes - literally, appeared over night. To the right of the trackpad, there's a section of blemishing, spreading over about a 1.5" area. It looks like a key has scratched it - except, there's no surface damage - only this mark. It can't be wiped off. I can't scratch it off gently with my finger nail. Washing up liquid won't shift it. The computer was pristine last night, I opened it up this morning and they were there. I live alone, and have no pets. Weird. Should I try a magic eraser, or does anyone have any ideas? I've heard toothpaste helps?