I have a Mesa single 50 watt head and the clean channel basically went out. One of the power tubes glows a blue tint while the other glows orange, but when I flip it to the lead gain channel, both glow orange but the tube that was once blue flickers and gives me a unwanted tremolo effect on my lead gain haha. I was just wondering if anyone might know what could be causing it, I was just going to replace the tubes (both power tubes) and see if that solves it.

TL;DR - My power tube is glowing blue and flickering giving me a unwanted tremolo effect, halp plox.

Much appreciated!