signs your pramp and power tubes need replacement

Having a little early fatigue from listening to newly aquired tube amp.
Could you provide a few more details?

What you describe could be almost anything. A list of associated equipment and a description of recent changes would help.
Thats not worn out tubes. Noise and high frequency roll off are the first signs of tube replacement. Swap in a mullard someware that will tame things down
I just bought a VTL IT-85 and I the sound is great very liquid..... but my ears started hurting, not good......... Thiel 1.5, PS audio plus spkr wire, Nordost Red Dawn Ics. The VTL just replaced a Mcintosh C15 and MC122 combo. Now I did check the tubes with a meter and the Ohms are reading 15 istead of 10........... the manual says to take it in for service with any reading other than 10............ the DC voltage was good. I guess I'm gonna send it to VTL. Does anyone know what the wrong ohmage reading on tubes mean.
Could be that the amp is biased a little hot. You might want to check the bias setting of the EL-34 output tubes. David Manley, the fellow that started VTL in 1989, suggests in his book that 27mA is the ideal setting for EL-34s and I have found that this setting gives that tube a nice rich sound. Measure the mV from pin 8 of each EL-34 to ground and divide that number by the value of the cathode resistor (Ohm's law I=V/R) to come up with the bias setting.