Downey Mildew or Cucumber Mosaic virus Help!

   A few of the leaves on my cucumbers are slightly mottled yellow.  I have been searching images on google and reading up about it.  At first I was convinced it was Mosaic virus but now I am hoping it is downey mildew.  If it is downey mildew should I just get rid of the leaves affected?  It looks like it is on 2 of the 3 plants I have grown  from seed    I tried to take some photos but my computer is not working well and I cannot up load them    Any clues on how to tell the difference between the 2 diseases and I am planning to treat it as if it is downey mildew as too depressing to think it is mosaic virus.  Is that silly?
Juliet