The reasons for this phenomenon may be multifaceted, and can be checked from the following points:
1. Could you please check if the incoming water pressure has decreased compared to before? If that's the case, you need to find a water company to check the water supply pipeline and pressure;
2. Please check if the valve in the pipeline connected to the water heater is opened smaller. If so, open the inlet valve larger;
3. Please check if the water outlet of the nozzle is partially blocked. If so, you can disassemble the nozzle and gently tap a soft object with the nozzle's water outlet facing upwards to shake off the blocked sand and gravel. At the same time, clean each nozzle one by one and then rinse repeatedly with clean water. For nozzles that can be directly disassembled, it is easier to clean them after disassembly.