We opened our pool a couple of weeks ago. I have vacuumed several times/ shocked / added weekly chemicals just as last year. The water appears clear and tests level on basic test. However, we have these fluffy clouds of tan on the bottom. When I vacuum some gets picked up but, seems to stir it up and it settles again. Our pool does have trees nearby. Maybe pollen? These pictures make it appear darker than in person. Any suggestions?