Chicken with leg issues

[FFPA]

We have a chicken that sometimes can't walk in the mornings. Her left leg just goes out from under her. I pick her up and put her in the lower part of chicken house with pellets and water and she is usually okay by the end of the day and the next day or two and then it happens again. We had another chicken that did something similar and eventually died. Perhaps some vitamin or something they are missing?

 

[Eggcessive]

Welcome to BYC. Could you post some pictures of the chicken when she is standing normally? A video could be uploaded to YouTube with a link posted here to see what she is doing. Are the legs straight on both sides, or does one leg (or both) have an appearance of bow legs or knock knees. Does she seem like one leg is numb? Was she vaccinated for Mareks? Have you added any new birds recently? B complex is a good supplement and can be crushed 1/2 tablet daily into a bit of water or food.