Thanks for all the thoughtful responses!
I have never changed or updated the drivers since I got everything running smoothly 2 years ago. I'm using a windows machine that's only used for this purpose and never gets updated. I've learned after some time that updating systems and drivers often causes more headaches than its worth! Now I never update things, and will dedicate a computer to a machine, if needed.
I changed over my machine for piezo around 3 years ago, without flush. But... It did take some time to get rid of the color cast. After discussing with Inkjetmall, I had to run additional power cleanings, and the problem was solved. Neutral prints from then on out. I was starting to feel confident in the consistency of my system
In general, I've been printing more and more Piezo for my clients, and everything was rather stable- density, neutrality, etc. After I refilled or topped off the inks (some carts had dropped to about 30% levels) I did do a power cleaning. I had just printed that image the day before adding the new ink (opened a couple of new bottles for this- noticed the color of the ink in the bottle shade 6, in particular, seemed strange, after seeing the drastic color shift of my print). The machine had been giving me consistent results for months, until bam... Things changed. I was right in the middle of making an edition for my client. I tweeked the curves and essentially explained there was nothing I could do about the color shift.