Dishwasher worked fine until about a month ago. Repairman said the machine works fine including thermostat and heating element. He said the water getting to machine isn’t hot enough. This is, again, a new problem. There is a designated valve to the dishwasher rather than shared with hot water to faucet. I have switched valves to see if there was any change with no luck. The dishes are dirty and wet at end of cycle. Water to the faucet takes about 40 seconds to heat up, which has always been the case. What is a possible reason this change has occurred recently. Would having hard water have anything to do with it?