Trying to diagnose missing Cyan ink with an Epson P900 printer. Nozzle checks shows NO Cyan ink nozzles at all printing, even after several cleaning routines. Cyan is completely blank in spite of the cartridge being half full. The ink tubing (without taking it apart) looks fine with no obvious bubbles). All other ink nozzles print perfectly. Prints of test images (like from northlight-images.co.uk) also show cyan missing. What could be causing the complete dropout of the Cyan ink? What else could I do to troubleshoot? What else might i do to to bring the Cyan ink back? What should I do next?