Dead tube or broken amp?

Dead tube or broken Amp?
This last few weeks I have noticed a big shift in the focus to left of center, and last night I got some nasty cracking and buzzing so I swapped out the 6CA7's for a set of EL34's I had from before.

First of all, wow, why did I ever take the EL34's out, they are glorious, but the stereo focus is still dominantly left, AND - now I notice one tube does not glow at all, but the other three do. All the preamp tubes glow too.


I am running a Primaluna Prologue with Nola Boxers, all the cabling seems fine, have I lost a tube, or have I lost some circuitry in the amp?
Just swap the tubes from left and right channels and you'll have your answer.