having to large of an inside diameter of a hose/pipe can be an issue,
and
having to small of an inside diameter of a hose/pipe can also be an issue.

to large diameter, and not enough veloicty (think MPH in vehicle) of how fast air is moving through hose/pipe. and the air will not move fast enough to fully clear out the hose/pipe.

to small diameter. and you are creating a lot of extra friction loss resulting in less air getting to the diffuser/s

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running air hoses up and then back down. U shape or even upside down U. can create spots were an "air lock" occurs. this can require much more air pressure from pump to push the water out.

diaphragm pumps. as the diaphragm begins to were out. and they do wear out. will create less pressure. and you may find after a power outage or turning pump on/off. that it will no longer pump air down to diffusers. if you raise diffusers up higher towards surface of water, the pump will begin pumping air to diffusers. more of tale tell sign that diaphragm is wearing down pretty good.

having say a tire nipple / valve stem for say a car/truck/bicycle tire plumbed in line, between your pump and diffusers, might help you quickly check air pressure and have something to gauge what is going on with the system.