We have brand new dark gray plaster and some areas are a very light gray, nearly white. I know darker colors mottle easily and we really like the mottled look, but in the spa it is just really bad. Like it wasn't brushed well enough in the first couple days. Same thing around some of the edges of the steps. Tonight I took a small piece of sandpaper and rubbed one of the white spots and it took it right off. I really don't want to sand the whole pool, so I guess I am wondering what else I can do to remove the milky areas. I was told that I can't use a wire brush one it.