Did your printer have ink or PiezoFlush carts installed while it sat unused?
Did you shake your ink carts before starting to print again (to get pigment back in suspension, after settling from lack of use)?
Are you saying the magentas and yellow channels are printing light on your nozzle check, or only a few nozzles are printing from those channels?
Please remove your ink carts to check the physical ink level.
Please let me know, so I can try to help you past this and back to happily printing.
Best regards~ Dana