I have these light goldish stains on the bottom and a bit of the sides of my vinyl lined pool. They don't brush off w the brush or pool robot.
They were there last year as well when I closed, and don't appear to be algae or growing . My FC is around 7-10, cc 0-0.5, ph 7.2-7.4, ch 100, cya 60. Temp 58-62.
How can I test if they're metal stains? If they are, Do I really need to bring the FC to 0 to get rid of them , or will they ever go away completely? Liner is about 8-9 years old.