If it is staining due to pollen, then it will come off with the continued use of chlorine. Another good idea is to get skimmer socks, or use old pantyhose to cover the inside of the skimmer basket. This will filter out very small particles. I had a friend use coffee filters in the skimmer basket to get rid of very fine dirt that had run into the pool. Can you post the rest of your chemical numbers? Pollen is really a pain with pools, it just takes a little more patience - when the pollen is over the worst, the bleach will get rid of any stains and the continued filtering and brushing will get the water sparkling again.