This sounds a lot like your yellow nozzle is clogged. By the by, Epson's nozzle clean/head clean just wastes ink in my opinion. Have you left the printer with the cartridges in not being used for a long period of time? That usually clogs the nozzles as the ink dries up.
You can follow a guide that I followed to try and clean the nozzles. It worked for me the first time, but when I did a second lot of treatment, something screwed up and I'm left with a very VERY heavy paperweight.
Guide's
here, if you want to take a gander.
Good luck and you've been warned!
- Malentine Bentley