I have a Hayward DE ProGrid 24 sq ft filter and a 1.5 HP pump for a 18,500 gal above ground pool plumbed with 1.5” pvc. I have a Blue Wave NE6171B Maxi 1.5hp pump meant for above ground pools bought in fall of 2020. I use 4-5 of the Leslie’s blue scoops of DE when I charge the filter. I just replaced all the grids because I was only getting about two pounds of back pressure before the flow rate fell to a trickle. 10 psi with no DE, 11 psi fresh loaded, about 13 psi and the flow rate has dropped by about 3/4. I haven’t done maintenance on the pump since I installed it. I also haven’t replaced the gasket in the Hayward multi-port since 2020 either. To me it seems the pump is failing to produce decent pressure under load. Is there anything I can look at/ replace in the pump mechanism? Or do I just have a cheap pump and need to shell out $$$ for name brand?