Jadis DA50 blown tube

I have used my DA50 for many years without problems. Recently one of the KT88 tubes blew out and there was no sound from the left channel. I took the amp in for repair and it came back working fine with two of the four KT88s replaced.
However, on closer listening, it turns out that the sound from the left tweeter is at a lower level than the right channel. The rest of the mids and bass sound the same. I switched the speakers around and made sure the problem was not with the speakers. I even switched the cables to make sure the cables are ok. The sound especially with vocals, is now skewed to one side. Any idea what could be wrong with the amp, or anything I can try to resolve this? Thanks for any advice.
Have you tried to switch the valves around? If the issue moves to the other tweeter, then the root cause is with the valves. Are they same brand and model?
I doubt I can help beyond asking a few leading questions.

Which two of the tubes are new? One per channel or half of each channel?

Any idea about the tube bias being set correctly after the replacement?
Is it significant enough to exclude the possibility that it was there prior to the tube blowing and you are just listening more carefully now? Possibly a symptom that let to the tube failure. Just thinking out loud.
There are two tubes for left and another two for right channel. The two left tubes are new and the same KT88s from Jadis. No idea about tube bias.
Actually I have a separate set of 4 Gold Lion KT88s and the same effect with these as well. So I don't think the valves are the cause.
On further listening, I think the entire left side may be a little weaker. I have tuned the Balance knob over to the left and it seems better. Is it normal to have different amplification levels on the left/right channels? I guess that is what the balance knob is for? I have always had it dead centre before.
Have you tried swapping the left and right on your source interconnect on the outside chance the amp is getting a signal that isn't even?
Good point. I will try switching the left/right from my CD source, thanks.