muscovy bill color

[fowled-out]

My black hen scovy just hatched out a few ducklings. I noticed 2 that have pink bills and the rest of the other 3 have greyish blue bills. 4 of my drakes have been working with her, 3 black drakes and a pied. what is the issue here?

 

[ian4379]

usually the more white in the feathers, the more pink on the bill.