Why would the hot water have no pressure in the bath tub but be OK elsewhere?
If new house and always did it with slab floor, it could be crimped hot water line under slab, something in hot side of valve and if copper water lines were used, i have seen the pipe go all the way into a tee, and it was blocking the water outlet line to faucet. If it is old house it will be most likely something in hot water side of faucet. I would call plumber. There are still other things it could be like temp. valves.
