Since I bought my mid-2015 MBP, this gunk has been staining the screen as you see in the picture. I'm not sure if it is scratched or what and I don't know how it got there. At first it was only on a small part of the screen but it has now spread all over the whole screen. It's not too bad when the screen shows lighter colors but really looks bad when the colors are darker or the screen is turned off. I went to a computer shop (there are no official Apple stores in the developing country where I live) and they hadn't seen it before and didn't know what to do. Cleaning it with a cloth did not work either. Does anyone have any ideas if I can get this off? Or is it scratched? Thanks.