During the last couple of days, my 3 foot sea horse mosaic, which is on the floor of the shallow end, has yellow staining around the edges, it resembles rust and will not brush away. What could be causing this and what can I do to reverse it?
I also have a couple of specs that come and go on their own on one side of the pool. They appear to be rust but will go away sometimes for several weeks and return. Brushing will not remove them. I put "metal magnet" in about a week ago for the small stains and like in the past, it did not help?
PH - 7.2