Air diffusers certainly keep the water column moving preventing the smallest particles from settling out. If the weather permits, turn off the diffusers for a week or two and see if clarity improves in that time. Then you will know for sure their contribution.
For my pond, after a good rain, I need a few days in a row with low or no winds for the clarity to come back. Not change at all while the wind keeps the water moving.
Also many here suspend their diffusers off the bottom a bit, putting them on something so they don't bring up sediment. Personally I would make a raft from a pallet and small concrete blocks so it will sink, and attach to that. Then you get a little habitat along with stand-offs from the bottom.
