We have a 21' above ground pool with a hayward filter (SM2106T in case it matters). The filter is about 7 years old. I recall having a slight issue last summer with cloudy water that wouldn't quit and now upon opening we are losing pressure and the pump/filter combo seems to be running quite low. If I backwash and rinse, the pump will run at full strength for a good 30 mins but then it dwindles down to hardly any pressure so the pool isn't getting cleared. I'm not sure if I need to replace the sand or if something else could be the issue. I've checked the obvious things like the skimmer basket, the pump basket.