Thanks for the additional information.
It’s important to print a nozzle check after flushing a printer to make sure 1. all channels are printing pink (ink is all flushed) and 2. all nozzles are printing, and is also good to print a nozzle check after the printer has sat unused for a while, before reinstalling ink. We have flushing instructions here: http://www.inkjetmall.com/tech/content.php?140-Flushing-Epson-Pro-and-desktop-model-printers-for-safe-long-term-storage-or-when-switching-inks
Did you shake the ink carts and make sure exit channels were filled with ink before reinstalling ink carts into your printer?
Do the lines appear light pink with PiezoFlush, or dark color with ink?
Have you done any C/VM paired regular or power clean cycles?
Since you didn’t print a nozzle check after flushing the printer, or before reinstalling the inks, it’s hard to tell when the C + VM channels stopped printing. The C + VM are paired in the print head, so share a damper and capping station. It could be that the damper needs to be replaced (all dampers should be replaced at the same time), or possibly the capping station didn’t seal or suck those channels well.
It’s also important to seal vent holes when storing carts out of the printer, to prevent evaporation or stuff from getting inside.
Please let me know, thanks~ Dana