We have a Catalina Mariah.

Some of the jets do not seem to be working fully. One seat has ones that have turnable knobs. I turned them to the on position. However, they still are not very forceful.

Another seat just barely works. This one does not have turnable knobs.
This one is about the diameter of 2.5 inches. In the center is a white plastic deflector with 3 sections. (kind of like a pie cut into 3 pieces).
I have tried and cannot get it to turn or anything.

How do I remedy this delimna?