Hurricane Sally's surge filled our (vinyl liner) pool with several inches of silt, leaves, and vegetation. The pool sat full of the brownish green water for a week before we were able to get it cleaned up. Only organic matter was found in the pool during clean up. We went through the list of shocking, over chlorinating, backwashing, changing our filters, etc... We were left with these stains that, to me, appear to be organic but don't seem to go away by applying chlorine directly to them. We recently tried Oxalic Acid just in case the stains weren't organic but it didn't help. Any help or suggestions would be greatly appreciated. Thanks!