The water pressure drops significantly when I try to adjust the temp. When I turn on the water dial the pressure is great throughout the cold/ blue, but once I turn it to HOT there's almost water pressure. This is the only discharge ion the house that has this problem. All of the sinks and the shower in the master bedroom maintain the water pressure regardless of temperature setting

What kind / type / brand of shower faucet do you have ? Single handle ? Back to you . Milo

Sounds like you've picked up some trash in your hot water system that's now clogging the inlet ports of your cartridge. Answer Milos questions and be prepared to shut the water off, open up the valve, pull the cartridge and clean the ports and then turn the water back on for a minute to flush out the supplies and open valve body. Reassemble and test. Good luck, Tom