I can do a normal clean followed by a perfect nozzle check on my 1324x. Then I can print a solid black for about 2ft and the black fades to a dull green. I repeat the nozzle check, and have a perfect CMY, but no black. A head clean then gives me another perfect CMYK. Rinse and Repeat. Same thing happens again. I have cleaned all lines doing a longstore, and then recharged the unit with ink, and the same thing happened again. The maintenance station and cap are clean, and ink is traveling well. Should I change the dampers (valve head assembly), and if so, is there a way to change them without removing the printhead from the machine?