Hi all, so I finally have crystal clear water after having algae. After about a week or so I noticed what looks like dirt/film around the interior of the pool at water level. I tried using a brush to clean it and didn't work. What can this be and how should I go about cleaning it? I will be testing. I'm currently letting the pool drop to a FC of 7, pool was at a FC OF 16 while shocking. I also know before shocking ph was over 8. Could that be a issue? I'm going to test TA and PH in a few minutes and will report back. Any help would be great.