It's one system. One Pump. [Tank -> Pump -> cold lines to faucets and water heater. Water heater lines to hot side of mixing valves.
If the cold faucets are good, but not the hot, there is an issue at or after the water heater. IF there is good flow to some cold faucets, but not others, there is an issue in the mixing valve, aerator or pipes themselves.
Start with the pump. Make sure it's getting full voltage and that the pump isn't slow do to corrosion on the connectors.
From there you have to follow the system. A blockage in the pressure system is incredibly rare. The only place it typically clogs is the aerator.
You might have an opening in the system somewhere, however you would hear the pressure pump cycle on and off periodically if that were the case.