Sorry for leaving out the fact that yes, it is a sand filter. I have not had any change in pumps and, as stated in my original post, everything worked just fine the first two years. Are there tests that I can have done to the system to see if there is a blockage somewhere? By the way, when I backwash, I normally fill the pool to the point where I can backwash for a good 15 minutes before the water level returns to normal.

Thanks for any tips/suggestions.