The hot water everywhere else is fine. The cold water in the tub is fine. The hot water in the bathtub is very low pressure. Any ideas?

The hot water everywhere else is fine. the cold water in the tub is fine. The hot water in the bathtub is very low pressure. any ideas??
You have some minerals clogging the hotwater inlet ports on the valve. The solution would be to shut the water off, open up the valve, remove the cartridge and check and clean the inlet ports. Before you button up turn the water on for a few minutes to flush out the supplies and valve body. Reassemble and test. This will just happen again unless you flush your water heater out on a monthly maintenance schedule. Ley me show you how. For long life and fewer troubles you should keep your heater clear of mineral build-up by flushing on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back togather the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps, Tom