Hi everyone, I just had a pool installed last year and the white plaster with the stones in it is already yellowing only on the first step where the water is only a couple inches deep. The builder convinced me to use no color, saying it made the best looking water. Should it be drained to that level and acid washed or can I soak a sponge with acid and scrub it under water. I see they make a kit for removing stains that connects to your vacuum pole with an acid reservoir that seeps into a rough pad to scrub the plaster.