You can add a tablespoon of brewer's yeast per cup of food and that has loads of B vitamins.
Not baking yeast, brewer's yeast. It's a nutritional supplement.
She looks like a happy duck aside from the leg problems. I would plan to make accommodations for her - and in the meantime, try to...
This has some helpful information https://sites.google.com/a/poultrypedia.com/poultrypedia/poultry-podiatry
But if there are leg problems, B vitamins are often included in the treatment plan. So far, what you have given them doesn't sound like they are getting extra B vitamins.
Can you get...