First, run a nozzle check to see which inks aren't printing properly. Then run the head cleaning utility several times more.
The Epson website states "If print quality has not improved after repeating this procedure about four times, turn the printer off and wait for at least six hours. Then run the nozzle check again and repeat the head cleaning if necessary". My own experience though (with a different brand of printer) is that it can take ten or a dozen head cleans to do the job.
Otherwise you'll need to attempt to clean the print head manually, possibly using a kit from here
http://www.printheadhospital.co.uk/
as explained here