I think you're on the right track thinking weasel or mink. They're very clever, can fit in such small spaces, and have grabby paws. Hope the chickens heal quickly and you catch your offender.
Also, it looks like you have them bandaged up well. They're in good hands, I have no doubt they'll...
If you do get a chance to post please do. I know sometimes the upload just doesn't work whether it's on my end or byc's. Are the other chickens missing patches of feathers like this one?
Good quick thinking. If there is no blood and you have it cleaned up I believe she will be just fine. Just keep an eye on her and let her rest a while. Give her some fresh water, food, and maybe a tasty treat to make her feel better about being in a new environment.
Next I would try to find...