Banding caused by slow cartridge on MP 780?

[akon]

My nozzle checks and alignment look good and everyday printing is fine, but when I print 8x10s I get banding that gets progressively worse throughout the photo. It has been a while since Ive purged my OEMs (hobbicolors UW8 and the Pigment black is Precision Inks). My thinking is a purging the cartridges should fix it, but wanted others opinions too. Does it look like the cyan is the culprit? thanks
http://img821.imageshack.us/g/10011.jpg/

 

[qwertydude]

Looks to me like a combination of your cyan and magenta, it's especially bad with the finer nozzle photo cyan and photo magenta. It could be a clog but more than likely it's a flow issue could be caused by cartridges needing a rinse but my solution for similar problems is adding a surfactant, I use kodak photo-flo and it works wonders in making ink flow into difficult behaving foam.