I have a problem with spots on my Ipad screen. First of all, I bought the special folia to protect the screen. It wasn't simply possible to glue it without having very unpleasant sort of spots. When I take this protective folia off from the original screen I see also other types of spots on this original one. Why,first of all, they appear and how to get rid of them?? Is it recommended to use the protective folia?