Hi, I have a RMBP 13inch 2015 model. I always take care and adore my machines and only clean the screen with a microfiber cloth. Recently I noticed such stains like these in the picture which wont go away at all no matter how I try cleaning it even with little water? Is this normal wear and tear as my machine is one year old or is the screen coating peeling off? Although when the screen is on, I can't see them.