Sometimes the problem may not be in the entire system but only hot water pressure. If you notice that you can't get enough warm or hot water, the problem might be with your plumbing system. The first place to start your troubleshooting work is to inspect the water heater.
Check if the outlet valve in your water heater is fully open. If the water heater is partially closed, that can be the reason you can't receive enough hot water flow. Open the water heater fully then return to the fixture to check if the hot water pressure is restored.