I have been noticing some blue (baby blue) spots in my white plaster. Can't brush them out. I don't know if it's my copper plumbing (the return/suction valves at the filter are copper, but a lot of the piping has been replaced with PVC, especially throughout the pool, return jets, etc.). Plaster is about 2 months old. I know the plaster company has used HASA stain out after the water was filled and recommends a bottle every 6 months.
Also, I have two brown spots that i cannot rub out with a stain eraser. Any recommendations on what to do next?