Our master bath shower had two shower heads. One was leaking/dripping so our plumber changed both cartridges since he was already there. That fixed the leak, but ever since one side gets too hot and the other side only stays hot for 5 minutes before slowly getting colder and colder. Our plumber seemed to feel that the two shower heads were connected in such a way that the first (hot) shower head got the water coming into the master bath first, and the second (cold) shower head got the water circulating in the bathroom last (after sinks, etc) and that maybe the hot water was dissipating before getting to the second shower head. I don't really understand. Does anyone know why this problem may be happening and how to fix it? Thank you!