Stains on vinyl liner of salt generator pool

[Mimi2Three]

Hi there. We had a new vinyl liner installed last year, and when we did we converted from chlorine to Salt cell generator. We kept the filter running about 8 hours a day all winter. We have no trees, but there was a brownish sludge on the bottom when we opened it. We vaccuumed it out and did all the start up stuff, and it looks great. But there are a lot of brownish stains on the slopes and edges of the vinyl liner, not so much on the bottom. The stairs were also a little rust colored, but I am solving that with vitamin c as I read earlier in other posts. Vitamin C didn't seem to budge the liner stains. We did put the salt on the steps to disolve it, so that is probably why the stains there. We are on a well.

Any ideas on how to clean the stains of the liner?

Suzi