Sand Filter/Pump problem - AG

Hi all,

We have a 2-speed Pentair pump and a Hayward sand filter on our 12,000 gal AG pool. It seems to us that this season the pump, when on LO, is not moving as much water as it did last year. Additionally, there seems to be much more fine debris on the bottom of the pool than there had been last season.

I've backwashed and rinsed the sand using a white pitcher to collect the waste water intermittently and I stop the backwash when the water in the pitcher is clean. I'm confident the sand is clean.

Putting a sock in the skimmer basket like last year seems to cause a problem as soon as just a small amount of debris collects in it: there's very little water coming from the return. We don't have a flow meter so I cannot define "very little". What I do know is that there's way more dog hair, tiny little flower petals from the trees, and various drowned insects floating on the water surface. Far more than last year.

Is my pump going out already? This is only its second year. Or is there an air leak somewhere in the filter?

If you could point us into a direction to start checking and testing the system we'd really appreciate it.