Is this describing a blown tube, or two blow tubes?

I installed a new set of JJ e34’s a few days ago. Last night there was a very loud POP and one of the tube went bright so I moved quickly and turned of the midmonos.

After they cooled I inspected the tubes and they seemed fine so I reinstalled them thinking maybe it was some kind of impurity within the tube. I’ve never experienced a blown tube before.

The amps ran great this evening until just now, and another POP and bright tube, but it seemed like it was the other tube, but I can’t be sure. This was followed by a low whistle or hum and I turned the amps off again.

Is this simply a run of the mill faulty tube? Could two blow in one day, or could the first one POP like that and then continue to work for another day?

Since Ive never experienced a tube fail before, could this have anything to do with the Amp, or is it just a bad tube or tubes?

Should I worry about putting my old tube back in?

Thank you,

TD