Your filter pressure goes up and you lose return flow even after cleaning?

Cartridge and DE filters are the most prone to what is commonly referred to as "short cycling". This is when you clean the filter and the pressure goes back up right away. Over time, debris gets entrapped in the fabric cartridge element or DE grid material and it can not be removed by backwashing or cleaning. You can try a filter cleanser but it would be best if you replaced them.