consider this.

[Unregistered-lg]

you’re going to notice low pressure more on the tubs because the faucets have flow restricters in them.
and also when a bath is being drawn then it’s more hot then cold water.
on top of all this i think you might have some old galvanized somewhere.
and what if the pressure is on the bottom end close to 35 at the time because everybody is watering the grass or taking a shower.
if it’s something you can’t live with then i would look into a booster pump.