We opened our pool this weekend. It started out very cloudy as I have a mesh safety cover and LOTS of silt had passed through. As of last night, I could start to see the bottom of the shallow end. My PH was through the roof and I am working to bring that down. I've backwashed twice so far. I've noticed, however, that the filter pressure after backwashing is about 4 lbs greater than it was last year. What might cause this?