Once you check all faucets screens to be sure they are clean , i would drain the system.
Then I would blow compressed air through the lines as well as the vent tube next to the gravity water fill port.
Have someone open each faucet one at a time to see if air flows out.
A dirty pump filter will reduce water flow and allow enough pressure for some faucets while not others.
When manufacturers drill holes in fresh water tanks to install fittings they sometimes leave plastic debris inside the tank. Over time , that debris can find its way into a system.
There could a clog at an elbow fitting where the compressed air might dislodge it while water pressure did not.
