We have been having some construction going on the last couple weeks(it is now over) so yesterday I did a good pool cleaning. I came across these rust looking stains in the pool in the shallow end. One is about a dime, all by itself. Then a couple feet away are a small grouping of them. I tried to scrub at them but they did not change. My pool readings are all good. I have been adding a metal solution once a week. I wonder if maybe some nails did not fall in the pool and sit for a couple days before my vacuum got them. I have not a clue how to get them off. I do have pebble tec and tried to take some pics of the ones that are grouped togeather. The are right below (far left) of the step - in that little nook). Can you see them ...righ there Anyone have an suggestions? Thanks!