One other thing to check are your shower hand wands.
If someone has forgotten to shut off the faucet valves in the shower (OUTSIDE TOO) and just closed the button on the wand when they finished their shower, cold water will mix with the hot water inside the valve body reducing the temperature of the water at the point of use.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW