Hi all - I'm sure this is a question that's been asked many times, but I figured I would ask again. We have yellowish stains by the water line on the stairs and in the spa, both of which are gray plastic/fiberglass, I'm not exactly sure. We have very hard water in our town, and the water softener does not soften the water that goes to our outside hose - is it possible these are hard water stains? When I had our water tested earlier in the summer they told me it was actually softer than it should be for a swimming pool. Or if that's not what it is, what else could be the cause, and what is our best solution for getting rid of it? I appreciate any help anyone can give!