So, to clean up some dirt/scratch marks on our walls, we picked up a couple Magic Erasers. I tried using the first one in a few spots on one wall, and while the dirt came off great, the next day I could see light black spots where I had used it. I'm not sure if it was too dirty or it's some kind of reaction to the paint. The paint is a semi-gloss white so at certain angles the resulting "stains" certainly stand out. Is there something I can do to help with this, aside from re-painting? I'm thinking it may have removed some of the "gloss", but I'm not sure why it would look light black.