Hmmm
Are you seeing signs of “breeding damage”, like missing feathers, or scrapes on her back?
If not, and your drake is a runner/ there are no heavier bodied male birds that have access to her, I personally doubt that is the issue.
An avain Vet is the best option, if it is an option, of course. We are just other keepers of fowl and are not vets!
If a vet is not an option-
Have you checked her feet?
Bumblefoot seems a much more like option to me. Sores that are often warm, have black “centers” or “splits” on the toes, or a big black spot on the base of the foot/ near a claw.
Can you please take some photos of the undersides of her feet and send them here?
If it is bumblefoot, we can coach you on that/ there is a ton of info here you can find.
Also, please feel her leg carefully, and move it, to make sure you don’t feel a break or damage that might have happened in a scuffle w another bird.
Durvet Vitamin B supplement is a liquid that you can get at most good sized feed stores- it’s not labeled for ducks but can be pulled up w a syringe (it is an injectable for goats, given orally to ducks over treats), and nutritional yeast from the health food store is another good option to increase vitamin B.
You can also crush up some “people” vitamin b tablets, but they can’t be time/ slow release or they won’t be absorbed. Crushed tablets can also be sprinkled over normal feed. Excess Vitamin B won’t hurt anyone, and may help w leg issues.
That said.
If it is bumblefoot, the added vitamin B alone won’t resolve the issue. You would need to treat the infection, and resolve the sanitation issues that led to it.
@Miss Lydia
Please send photos of the bottoms of her feet when you can -
@Farmgirl283420 - same goes for your chicken....
Although the B vitamins are not as critical for chickens as they are for waterfowl.
You might want to start a separate thread and tag me in-