After printing off several 13 X 19's with zero issues, I performed the weekly head and ink/cap unit cleanings. I ran a nozzle check and found some irregularities; I then ran several head cleanings. After each successive nozzle check, the C block disappeared completely while all of the others came up fine. I'm still using OEM inks until I run out, after which I'll be using Cone ink. BTW, I checked the paper towel after doing the head clean and I'm certain there was nothing left behind after I pulled the paper out.
Am I missing something here, or should I continue with the head cleanings?