I think that the plasma color presents itself as normal. You don't want to see any hint of peach, pink, or orange. It should be a light violet - close to lavender, or a white washed violet. The nitrogen gas fill in the tube would be normal then. Your Helium and CO2 fill should also be okay.
This is tricky now. I thought the color would be way off. But you've got 22mA through the lavender plasma, the only thing that could hold it back is a dirty output coupler.
If optics appear to be fine, and the current through the tube appears to be stable and the optics are clean, there are only two things left:
Gas mix appears to be fine, but is still off - a slightly bad gas mix could greatly affect power, but its strange to think that a sealed glass tube has "suddenly" began to leak come to pressure.
The optics are mis-aligned. While the tube is supported on only two supports on either end, try giving the tube a light press down in the middle (where its not supported) to see if power changes. Rotate the tube some 20 degrees and try again. Keep doing this until you otherwise see a change in power.
I'm not entirely sure what could cause a tube to suddenly become mis-aligned, but the odds of it happening are much greater the longer the lasing cavity is. A 60W CO2 laser has a significant length to it.
See what happens after you clean the output coupler and "bend" the tube around a bit.
Do not break that tube.
