The cartridges should be cleaned once a season with a degreaser or acid bath.
Body oils are the first things to clog a cartridge element. A degreasing solution should be used to remove oils. If an acid bath is used to remove oils, it will embed these oils into the fabric and make the element less effective. Your local pool/spa dealer should have a cartridge cleaner.
An acid bath is for mineral deposits on the elements. If an acid bath is needed, do a degreasing wash first, then the acid treatment. Start off with a mixture of 1 part acid to 5 parts water in a bucket.
ALWAYS add acid to water, never water to acid. If the mixture does not clean the elements effectively, increase the mixture to 2 parts acid to 5 parts water. Follow the proper disposal of the acid mixture, as per the acid manufacturer’s instructions.