About a week ago, our 2 showers both stopped sending hot water. We would get maybe 2 minutes of nice, hot water, then it would gradually get colder very quickly! We can turn up the temperature on the control handle (single-handle Price Pfister Avante shower control), but it still keeps getting colder. My husband pulled the anode rod out of the water heater - a little corrosion, but still good. We've drained the tank twice (50 gallons each time). Checked for proper pilot light and burner operation - all fine. We've checked under the house and the hot water line is HOT all the way from the water heater to the end of the line at the sinks and showers. All of our sinks get hot water just fine. The showers do not. We just replaced the cartridges in both showers (old ones still looked fine - had been replaced several years ago). We also have a circulation pump on the hot water line - we can hear it run - don't think anything is wrong with it since we get hot water at the sinks. We've removed the shower heads and turned the water on. Plenty of water comes out, but same problem with the hot water. Any thoughts? Our brains are fried now.