I would first do as Paul suggested and print the ink separation page in calibration mode set to 100. I would even crop each strip in the ink-sep image and print them at each of the ink limits that are set in the ink descriptor file to see if there is any problem with the raw grey ramps for each channel. (it will also show you if there was a problem with the inks being loaded incorrectly (been there done that a few too many times myself)
I thought I was having a similar issue with the head alignment but it turned out that I was printing too close to the top edge of the page. It seems like a 1-1 1/2 inch top and bottom margin are needed with these printers. I never had that problem with larger format printers. I have done multiple head alignments (6 maybe?) with the EB-6 inks and finally got it dialed in, the lines weren't too hard to read without using the color inks so I would try that as well (i never bothered to install the claria inks, and when straight to the cone selenium k6, and then on to EB-6 inks).
If one of your channels is blocked, you will still be able to get a great print from using only 4-5 channels. These 1.5 picoliter printers with the MIS inks are super smooth, and are one of the best buys out there for modest size prints.
Richard Boutwell