Guys, I've been through 3 Ascorbic Acid Treatments with my pool and am still seeing stains come back. I have a vinyl liner pool that holds about 13,000 gallons. I've tried water replacement and a CuLator filter in the skimmer. I've also cleaned off my cartridges in my filter to remove some of the metals. Each time it comes back seemingly identical to the way it was before. There are even spots on my liner that get darker stains than others, and those spots come back looking the same each time. Any help would be appreciated. I don't know what else to do at this point. Could it be some of the metal fittings in my system are the source of the metals? I'm using municipal water and the problem appears to be iron.