Weird Feather Loss on Chicken's Chest?

[greencow]

Is this molting? My BR has this weird cut thing on its chest. It stayed the same size for a while an now it's gotten larger. All of the chickens get along really well and haven't had any health issues.

 

[Mountain Peeps]

Was your bird recently broody? During broodiness, they pluck their feathers from their chest.