Poor quality in middle of print image

[bsamole]

I have Canon i960 the first 1/4 inch and the last 1 inch of a printed image on 8 x 10 paper is perfect however the rest of the image is slightly of over banded with a light magenta color. Since new I have always used Canon brand cartridges. Since the first and last parts of the printed image are perfect I don't know if replacing the print head would resolve the issue. Has anyone experienced this issue or any thoughts?