You are dealing with bumblefoot as you indicated by the dark round scab on the bottom of her foot. It is a staph infection in the foot caused most likely by a small splinter that has become infected. Once the staph infection works its way to the legbone, it quickly spreads throughout the...
For both posters: There could be several issues or a combination.
Inspect your bird(s) for lice/mites, either could be eggbound, or they might have worms.