out of curiosity, for diagnosing/direction.... what caused you to replace heads in first place?
my best-guess, without knowing for sure, is that you replaced the heads due to similar situation, heads not firing all nozzles, but the problem might not have been in the printheads themselves but the refreshing of the ink-siphon that feeds them.
The top 3 places you can lose suction that draws ink through the system, would either be the fit between the capping station and the printhead, a cracked manifold (black part on top of the printhead, with the nipple that inserts into damper), ooooor you have a rotted/cracked inkline within the ink pump mechanism.
Cracked manifold is typical of fiddling with/around the dampers, while the ink pump/capping station happens from longtime wear/tear of the machine. all 3 are easy fixes, but diagnosing/narrowing-down is a process.
edited: if cyan/yellow are BOTH not working, then that might be an easy diagnosis..... as they're both tied to the same ink pump. 2 pumps operate the system, and i believe they operate KM and CY respectively. try simply swapping the lines between the two ink pumps to confirm. ...and then order a new ink pump.
