My bath tap which has the hot water is not working , initially the flow got gradually decreased until one day it totally stopped . All the other taps with the hot water are functioning normally

Two handle faucet or one. If its one you have a cartrridge mostly and the inlet port is plugged with debris. Power flush your water heater more often to avoid this. Do you know how to remove the cartridge and clean? If not try to give us a brand/model or picture.