So I have at least one, maybe another. It's bad for transistors right?

My teacher took the amp apart a while ago, and it got the nasty shrill, but relatively quiet whine shortly after that. Could it just be that something isn't attached right?
Or are my tubes actually done. I heard it could also be caused by poor connections, or other things like that, not just bad tubes. They are a little over a year old.

I'm taking it to my teacher friday, but can anyone help me understand more?
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