Frostbite or Pigment?

[little redhead]

Hi guys, I live in Eastern NC, so it's cold right now with some snow and ice but it's not COLD, ya know?

I have a 1 yr old Rouen hen (among a drake and 3 chickens). They have a 16'x 16' open air coop with run-in and have lived there their whole life. While feeding, watering, adding bedding etc., I noticed some dark color to her webbing that wasn't there before. Am I seeing frostbite or just a pigment change? Here are a couple pics...

None of the other birds have it. Any clue, y'all? They are in my laundry room right now just in case.

 

[little redhead]

sorry. double post.

 

[little redhead]

Any advice? I have attached pictures.

 

[Eggcessive]

Have you tried posting over on the duck thread too? You may get better advice there about ducks. Here is the link:
https://www.backyardchickens.com/f/42/ducks