I had an issue last summer with metal staining that I was not sure of what the source was. It was either algaecide the pool company dumped in or Poolife Brite Stix I used for a bit. Both of these contained copper. This year there was no algaecide put into the pool and I forgot that the Brite Stix might have been the culprit. I used a few over the past week or so and now the stains are coming back lightly. I'm guessing the source is the Brite Stix. They contain 1.5% of Copper Sulfate Pentahydrate. Is this enough to cause metal stains on a vinyl liner?