Having issue with multiple showers

[Researchjay]

While in my master shower the water is hot. However, you turn on a second shower on and my master shower gets hotter and the second shower stays cold. When I turn on a third shower the second shower now gets hot, the master shower stays hot and the third shower stays cold.

Why does my master shower get hotter when I turn on the second shower? And why does the second shower only get hot if I turn on the third shower?

 

[Geofd]

Are your faucets in those bathrooms affected the same way??????

 

[breplum]

if you have pressure balancing valves on any of your showers, it is likely that one is the culprit.
to check, turn off cold supply at WH and open any hot tap. if there is continuous flow after it depressurizes, then that means cross connection from somewhere.