I swam in the pool this weekend for the first time this season. Swimming with brush in hand to get those hard to reach places [emoji3]. I noticed on the steps in one area I had maybe 20 copper colored stains the size of peas from fertilizer. The brush did nothing to remove the stains. Does anyone have a recommendation to remove set in fertilizer stains from plaster pool surface? Preference not to partially drain pool but I guess I could...maybe muriatic or CLR?