I have a spa that overflows into the pool over a rock ledge My chemical levels are good, water in the pool looks amazing, but I keep getting a yellowing on the half circle that backs to the pool directly under the ledge. This yellowing is nowhere else in the pool. Could this be algae form inside the overflow ledge. There are lots of nooks and crannies in that ledge that I have green algae in the cracks. I scrape these the best I can but it bneer gets it all, and I can't scrape inside the cracks. Pool store guy suggested pouring shock directly into the spa after brushing the ledge and letting the water flow over, possible even turning on the blower to get even more movement. Any help would be great.