I recently had somebody come and empty a fire pit and they did it a little too close to the pool and I suspect there’s ashes in the pool now and I can’t get them out. Honestly, I’m not sure if that is exactly what it is. It looks like blackish, grayish whitish, depending on the light. Very flakey and thin. They’re most noticeable at night, but I have seen them during the day on occasion. I don’t think they’re green or anything. they are Approximately an inch in diameter and evenly spaced across the pool. I have a regular pool service come every week. They test the water. They vacuum. They clean the filter. They skim and they add any chemicals required so I don’t believe the pH is off or that there are any issues chemically. I have also tried skimming with a very fine cloth, which seemed to help for a minute, but it keeps coming back. Any ideas on what this is and what I need to do?