After opening the pool a few weeks ago, there are dark stains in various spots on the bottom of our vinyl liner. Some are long and others are wider and short, mostly in the shallow part, but one spot in the deep end. The pool opening people say they are worm spots. He said when they opened it, the found dead worms in various spots on the bottom. They have increased the chlorine levels in the pool. The spots seem a least bit lighter, but not much. What can be done with these spots? When the pool people put some granular chlorine on some spots, it seemed to lessen them a little. Is there anything else that can be done? It has been two days since the chlorine has been increased. Will these spots go away? Is there anything else we can try?