Tube newbee question

After 30+ years of solid state I now have a bran new Octave V70se currently running sed winged KT88's. I noticed 1 tube glowed a much a brighter blue than the other 3. 2 nights ago (day 5) I also noticed the blue would flicker with the bass. I turned the volume from a 9 o'clock position to about 10:30 when 1 cornor of the tube seemed to get super bright - then a bright blue flash occured with the Octave going into protection mode. Also heard a thud/pop from my right speaker. Recycled power and verified that the bias was set corectly - which it was. I left it in for a couple more hours and it still works but has a much brighter blue glow to it. Octave included a spare KT88 and the next moring I replaced that 1. Well that spare tube also has a brighter blue side. Note I will not put that original back in. Today I swapped that tube position to another and it still has a brighter blue side in the different spot. Today is day 7. So for now I have to assume I had 1 bad tube. My question is seeing a KT88 or even 6550 that glows a brighter blue than the rest a problem to worry about? The last thing I noticed is that both tubes that glow blue brighter needs to have the bias turned lower. The tubes are supposed to be a match quad set.

I also have a matched quad set of EL34's and a matched quad set of 6550's on order. All are factory sed winged c's. I want to eventually pick a favorite tube which is why I got the other sets.

Last my Octave dealer forwarded my concern to Octave and we are waiting for a response. I would like to get any opinions if this is something to worry about.

THANKS