Earlier this summer we had the concrete deck around our fiberglass pool redone. The workers dropped some metal parts in the pool, causing some rust stains on the bottom (picture of one stain attached). To try to fix it, I dumped ascorbic acid in the pool, followed by Metal Free (or something similar) per the directions. It did nothing for the rust stains, and a few days later the entire pool surface turned yellow. We realized that was an overall metal stain, so we did cycle after cycle of ascorbic acid (which did work on that overall yellow staining) plus sequestrant, but the staining kept coming back. At one point I also bought a CuLator bag for the skimmer (not sure that did anything, though) and did a couple rounds of adding cellulose fiber to the skimmers and cleaning the filter a couple days later (both times we did that the filters/fiber were orange from the metal staining). We have that issue mostly under control now (though I do sometimes still see a small bit of overall yellow staining), but throughout that process I started noticing these dots on the pool steps (pictures attached). They look like rust dots. The Leslie's guy told me they look like black algae, but they're reddish and I just don't think that's correct. Any thoughts on what they are? Is there anything I can do for them and/or the bigger rust stains on the bottom? I've rubbed Vitamin C tablets and chlorine tabs on the small dots with no success, and I've also tried resting a sock filled with ascorbic acid on the larger stains with no success. Any help would be so appreciated!!!