I have a Chipless Epson C5210 printer, after approx. 25,000 prints the cyan was printing lighter as I used the printer.
I am recently retired from the commercial printing industry and have watched press operators tweek their ink on a press
by adding a little black or other color. I added some black to the cyan cartridge and BOOM, it fixed the problem.
The prints are darker and look like they did before the problem.