It looks like she’s just molting! Sometimes chickens will get white feathers without reason. My GLC went through the same process. Now she has a very white head. The white on her neck looks like the casing for the feathers. That will fall off and look like dandruff.
So my Coturnix quail hen has started laying fertilized eggs. I collect them everyday, so she doesn’t have the opportunity to sit on her eggs. If I️ left them in there, would she go broody and sit on them? I’m new to Coturnix quail so I’m not quite sure if they are good parents.