How to handle infant mortality of Svet 6550C?

Purchased from Vintage Electron,one tube died,out of an octet purchased for my ARC VS110.Tubes were used by me for a total of 4 hours,bias checked metculously after every hour after warmup with no signal.
The dead tube took a resistor with it(hopefully not more-remains to be seen).
My question is:What kind of refund/compensation is in order here:Can I return all 8 tubes?Who is responsible,etc.?
Thanks,Raanan