This what a Piezography K7 Ink Separation printout should look like (this specific printout was made with a R2880 printer, using Neutral K7 ink on Hahnemuhle Photo Rag paper).
I wrote the K7 shade # on the left side, so you can see the shade/color position and density differences of the shades. There should be a noticable difference between each shade, as shown below.
What does your printout look like? Based on your resport, it sounds like a cartridge may have accidentally been mis-filled with the wrong ink shade.
Please let me know so I can help you sort this out and get back to happily printing.
Best regards~ Dana