It sounds to me like a case of an overloaded power supply degrading over time. Thankfully the modules should be protected against the adverse effects of this kind of thing. Some heat is okay, both on the modules and the power supply, but if it gets hot enough to burn a finger or anything like that then something is definitely wrong.
A power conditioner probably won’t help in this case – unless you were seeing some kind of scrolling (i.e., AC line hum) kind of noise in the signal path.