I have an 8 year old IG pool with built in fiberglass steps. I've noticed that over the last couple years that round black stains about the size of a dime or a bit smaller, are starting to appear on the steps around the edges where the steps meet the vertical wall of the fiberglass steps. I assume that there is some kind of hardware under the steps, buried under concrete, that are rusting through.
Has anyone experienced this and is there anything I can do to stop this bleed through?
I can post pictures if that would help.