Last year I did an acid wash on my in ground (fiberglass I think) pool and ever since then the walls of the pool continuously get dirty with either brown or green stuff on them. It vacuums or brushes off but is a pain to keep up with. Did the acid wash make the walls more porous and it's now trapping stuff it shouldn't be? The pool chemistry is fine and plenty of chlorine and the water itself is clean but the walls are not. Is there something I can do to address this issue or are the walls now ruined?