My husband and I just bought our first house a couple months ago and are having problems with our shower. The house is only about 5 yrs old, but the shower seems to get colder and colder every morning. We have plenty of hot water in all of our other faucets. One person suggested replacing some cartridge, but I can't find any more info on it. We have a single knob shower and it won't turn any further. Does anyone have a suggestion? Thanks!