That might not be a bad guess. I updated a previous post on the subject. I was able to wash my "scuff" off with soap and water and an abrasively textured washcloth. A dry polishing cloth did not work. My iPhone goes into the bathroom with me when I take a shower or soak in the tub so it can be my music player. So in my case my iPhone does get subjected to high humidity for a short time each day. If this is a fungus I think I caught it in time (thanks to this forum) before real pitting could occur. There is no way I could have actually scuffed the iPhone in the conventional sense. Not in the location where the stuff was located on my iPhone. I think when my daughter gets her SE I'll take my old iPhone 5S back to use as an iPod in the bathroom.
I did throw away one of the leather cases to my old iPad mini because it got covered in some sort of white fungus. I don't consider my area to be particularly humid but in my last house and in this one I've had a hard time keeping mold out of the air line in my aquarium and encounter mold more frequently. It wasn't a huge problem before when I lived in close to the city but the closer I've gotten out to the agricultural area the more battles I've had with various kinds of mold.
