Hello plumbing forums, I was wondering why the tile surrounding my toilet is gray in color. This seems to have appeared within the past year or two and I'm unable to remove it with pinesol, clorox bleach spray, comet, water or hard scrubbing with bristles. I'm guessing it might not be on the surface of the tile, but perhaps it's some trapped moisture/mold underneath the tile...what do you guys think? My brother seems to note that the bathroom in which this toilet is in will start to "stink" literally a day after I deep clean it (with pinesol, comet, etc.) I don't know if it has something to do with those gray spots....or because it's a bathroom...lol.