I've noticed a few stains on the floor of the liner. I rubbed a vitamin c tablet on one of them, and pic 1 (taken under water) shows what it looked like afterwards. I had to rub quite hard for a few minutes for the stain to go. I am not sure if it was metal or not.
This pic shows an example of other stains dotted around the pool floor. I think they have gradually developed over the last season. I was using Trichlor until a couple of weeks ago, and suspect my pH was < 7.
Any suggestions on how to get rid of the stains?
current test results