Oftentimes a particular cartridge can become dried up if not used for a period of time. Epson's were notorious for this several years ago. Not sure if they've resolved the problem or not. That could be the problem with a particular color. It is also possible that the seat where the cartridge sits has become clogged. Remove the cartridge, use a q-tip to clean the area and then replace with a new cartridge. Those tricks will usually resolve those type of issues. Good luck. Nothing more frustrating that the printer not working correctly.