Hello! We recently moved into a home with a pool. We have an above ground salt water pool that operates on a Hayward System. We have already had to have the salt cell replaced (less than a year old), We had a case of black algae that I think I cleared up, and now we have some type of stain on the liner. I tried the vitamin c tabs to see if it was a metal staining but it didn't respond to them. We also can't get our Chlorine level up when testing. I'm very frustrated because I'm not sure what I'm doing wrong.... help please!!!!