If you have not done a "powerful clean" I recommend trying that, then a nozzle check. If the trouble persists print a page of only Magenta, then another powerful clean, then do a nozzle check. if it is still there call Epson tech support. Not much else you can do.
While this one missing nozzle may have no visible effect on most photos, it is evidence of something incorrect and should be remedied on the chance that it could get worse.