I had greenish algae on the walls of my pool in mid June. Eversince then, I have been watching for it to come back after I treated it. During the last 2 days, I noticed a yellowish tint on some parts of the wall. I thought it was just shadow from the shrubs and trees nearby. I touched it and it did not feel slimy. When I brushed the pool today, I saw little clouds of dusty stuff coming off some parts of the walls. I wonder if that is the beginning of yellow algae. When I had algae before, it was greenish. After I brushed, I still see some yellowish tint on the walls. My test result for CC was 0 this morning so I wonder if something is causing the stain. It is easier to distinguish the difference on the steps. The top of the steps do not have the yellowish tint but the sides of them do. Not all of the sides, just some. Had this happen to anyone else?