I've cleaned my canon S750 printhead (amonia/distilled water -easy) and all colors now work well EXCEPT yellow. I get strong bands, 1/8 inch wide both on the nozzle check (other three inks look fine there) and when printing a photo where I get alternate bands of yellow and green 1/8 inch wide. Are the yellow nozzles wide open - or what? Could the driver be screwed up? More cleaning? Any help here? thanks.