Had a battle with black algae this spring. Between heavy brushing and high chlorine, finally declared victory, but the down side is that suddenly 3 or 4 of my in floor cleaning nozzles (Parmount PV3 models) now stick up and won't drop back down or cycle no matter how many times I tap them down. Took all of them out and cleaned them, but they still stick up every time, like the dead black algae maybe gummed up the works. Any suggestions?