Has anyone encountered something like this? Stain/dirt INSIDE the screen? I have a Macbook that wasn't used for a month and was stored on a shelf (nowhere wet/humid) same place it's always been at for the past 2 years without a problem, and when I powered it up today, saw this brownish stain at the screen's lower half. It's definitely inside/under, the screen's outer side is clean. It doesn't look like molds... I'm not exactly sure what it is, what caused it, and how to clean it up- any advice? Thanks!!