My pool guy just cleaned my cartridge filters and it hasn't even been 2 weeks and my flow is down to nothing with PSI 10+ higher. This is a recurring problem, I always have to clean the filters myself once or twice a month in between the 3 month cleanings the pool guy does (3 months is average for the area he says). Tried swapping in completely new filters, same problem. Pool looks fine, no visible debris or algae, no one has even been in it in 6 months, numbers are all perfect. Any ideas? Only thing I can think of is I had a 4x2' patch of pebble tech plastered on part of the spa to fix a leak in a rock feature last year, is it possible for new pebble tech to shed? I can't visibly see anything.