If the leg just seemed injured, I would also worry about possible Mareks disease, but that is only a possibility. Usually, Mareks would not suddenly affect 2 birds at the same time.
Did you find out the cause of the wound on the chicken that died? Could this hen that is sick have been injured as well? I would look her over for lice and mites, and treat her with permethrin 0.5% spray or dust. Feel of her crop to see if it is empty and flat, full, hard, or puffy like a...