Rouen duckling with no yellow fuzz

[Tiffrz-N-Kidz]

Hi all!
One of my rouen ducklings has no yellow stripes on its face nor anywhere on its body for that matter. The only 3 ducks we have are 2 female and 1 male and they are definitely Rouens. Is this normal?

 

[dumb_cluck]

Picture?

 

[Duckles]

I posted a pic of one of mine a while ago. As a baby I thought he was a cayuga because he was all black with a little priest-like white collar. Not one yellow feather on him. He is now undeniably a rouen.