We got a colored plaster pool. It had black algae so we chlorine washed it. It was a hot day and I think the chlorine baked into the plaster. We re-filled and the plaster looks really bad, like bleach in areas were it dried. We tried to acid wash a section of plaster on the step, but it did no good. We tried to sandpaper section and it helped a little, but not much. Any suggestions other than re-plaster. It looks horrible.