Thanks for the additional information.
Inks should be agitated more like every week or two- every month or two like you have been doing is not often enough. I agitate inks in our 7880/9880 printers by quickly rolling each side back and forth several times, and watch the ink slosh around in the carts to know the inks are being well agitated, but I don't do this with our 7900/9900 printers because of the printer and cartridge size- with these models I remove carts, then quickly tilt up and down several times to agitate ink in each cartridge.
Keep in mind that pigment settles to the bottom, and looking at your order history, I believe you are using the older 700ml internal bag cartridges (correct?), so ink is drawn from the center of the cartridge and not the bottom like most other model carts- therefore if your pigment is settled to the bottom, you're drawing in thinner ink with less pigment, which can certainly effect the color and quality of ink output.
If settled pigment is your problem, then it's typically resolved by removing and thoroughly agitating all carts, then doing an initial fill cycle to purge settled ink from the printer's internal ink lines and get full density ink from the shaken carts to the print head. BUT- if you have been printing a lot with settled ink, then the pigment/solvent ratio is off, and you have been printing with more solvent than pigment- therefore if you agitate now, it may not be exactly the way it should be (that would be more pigment than normal).
**Keep in mind, this is just a FYI- without being there to see your carts (seriously settled ink will show noticeably thicker pigment on the bottom of carts) or know the overall history of agitation, use, etc... I can't know from here if you are experiencing this, but wanted to give you the information and explain the importance of regular agitation.
Yes, the instructions for printing targets is the same- no adjustments to the target images, and printed with absolutely NO color management and the specific settings listed in our instructions, depending on if you're printing on gloss or non-gloss paper. My offer to make you a new custom profile is a test, which is why I suggested we try one to see how/if it effects your output and corrects your red problem. If it works, we'll make new profiles for the other papers you're using, but if it doesn't work, then I suspect you're dealing with settled pigment from infrequent/insufficient ink agitation.
We carefully test every batch of ink for quality and consistency, so there's absolutely no problem mixing different batches of ink together- as long as you're careful to fill/refill the correct ink into each cartridge, and shake the ink bottle before filling/refilling carts (as well as regular agitation of the carts themselves between refills).