The best way to remove the diaphragms is to firmly squeeze the soft portion between the upper metal portion and the plastic actuator body.

Pry in one direction, and once the diaphragm is released at one edge it can be pulled off entirely.

Inspect the inside of the actuator body and clean if necessary.

Replace the diaphragms with the new ones, and coat lightly with synthetic grease like the dielectric grease used for spark plugs; this will help preserve the rubber.