To retube or not to retube?

I have a BAT vkp-5 / VPI TNT JR W/ BENZ Ruby H, I have noticed about the last month that the left side is a little lower in output into the pre amp. I know I could change the right/ left tonearm cable to the cartridge which would really tell me if it in the cartridge. What keeps me from doing this is I dont have the best eyesight and hands are very rough. I have allready broke one tonearm cable.
Thats why I am asking this question am seeking imput on if the vkp-5 needs new tubes, is this a sign it should be retubed. Seeking knowledge before I start to experiment.
The other source`s are fine on balance tuner/ cd. David
Rather than swapping at the cartridge end, why not swap at the other end? That is, swap the RCA connectors at the preamp.
You might have to swap the tonearm cable as well as the interconnect to preamp. If you swap channels on the tonearm cable, and the low output moves, it's in the cartridge. If you put the tonearm cable back, and swap the interconects from p5 to pre, it's the phono stage. I believe your p5 has a internal balance adjustment, call BAT to be sure.

Honestly, it's hard to say on tubes or not. You really should try the above. It's less work than taking off 24 torx screws and tube swapping...

Are you running stock sovtek tubes? If so, retube it if you want better sound quality. Better 6922's and 6sn7's will make a huge improvement. However, the 2 6922's on the 1st input stage are very critical for matching. Again, call bat, they will walk you through it.

I recently retubed my p10se. Wow....big diff.
Jfrech I have it set on 56db gain I also run the RUBY at 100 ohms, I know thats a little lower than others recommend but thats what my ears like. Back to the tubes yes they are original probably w/ 1000 to 1200 hrs. Tubes are next on my list of upgrades and was just wondering if this is a characteristic of tubes when they get a few hrs on them. Buy the way Jfrech what did you retube the p10se with. David
The simplest way to find out if one of the tubes is out of order is to exchange the pre-amp tubes places: put the rigth channel tube into the left channel and do the opposite with another tube.