I have a roland VS 540 and when printing color tests for a job I noticed that my yellow is printing in muddy tones. I performed a manual cleaning and 2 powerful cleanings and did 3 print tests which show no drop out...but there are small black bars in yellow. There is also cyan (a little) in magenta, and lt cyan in lt magenta. The biggest contamination is with the yellow. Does this sound like print head damage? Should I keep printing to flush out the color? I do have a cleaning cartridge, although I have never flushed a line before and am not sure how to do it.