So a couple of months ago I got these little fellas:

 

There was NO yellow AT ALL in their faces. Pure white.

 

But now they're going through their first moult and this is what they're looking like now:

 

 

See the yellow? (the pics don't really do it justice) At first I thought it might've been something Charlie had been eating as he was the first to show it, and then Alpha started getting yellow bits and now they're both getting yellower and yellower. And you can see that the pin feathers coming through are yellowish too. So I'm more than a little surprised!

 

What mutation is this? Is it type I or II YF or something else?

type 1 yellowface. The babies most time have a faint yellow mask.

 

lucky you