I agree that they look like pen feathers. I have a little frizzle rooster. I think he always looks like a ragamuffin. Since he has his own hens, he is a little worse looking. They scoot up against him on the roost and over groom him.
Hopefully your girl is just going through a molt.
She is a beautiful girl. I hope she will be ok.
I'd offer her some canned fish for protein/feather growth, or some egg.
Is it wet and muddy there? Have you ever treated for coccidiosis? Do you see any lice egg build up around the feather shafts?
I had a little legbar (one of my bring- them- all- home -they have- pasty butt rescues) who failed to thrive. She lived almost two years but never laid an (external) egg. She weighed about 2lbs but she loved my giant rooster. I had to seperate them. I hated to do so, but his weight would have...
I'm behind on this thread, so I'm not sure where this is headed, so I hope I don't offend.
I love the mixed chickens. Every single one looks different from the others. I can tell my pure breed girls apart, but I usually have to look twice. I also feel like my mixed babies are very healthy...