what did you clean the electrical connectors on the printhead with? we have some cleaning sponges with our latex machines, we have had issues before when we have not properly cleaned the printhead connectors and the inside of the carriage where the printhead slots in, make sure all the electrical bits on both are cleaned then perform a hard clean and maybe a manual alignment, (if you can do that on a 26500?) not sure but i know you can on the later models. also i agree with the other comment don't forget about the magenta as sometimes it can look like one colour but it can be the other that is the issue.