New pool owner here and first post. Thankful I found TFP. Leaves and algae were left in pool over winter and left a mess after opening, but a couple week SLAM was all it needed. However I have these remaining stains on the liner (and the steps are stained brown). Is this easy to assume it is metal? Or could the leaves stain? If metal, what are your suggestions to treat? I've heard vitamin c tabs, but how do you do that when in the deep end and in a lot of areas in the pool? An old bottle of metal out came with house, so I assume it was used before.