I've never seen a bird with down that's any color other than white or grey. Baby birds get down before feathers and its always white or grey and stays thst way through adulthood. When your bird molts you will see some fluffy whitish down molted along with her green feathers. As long as she's not plucking her feathers, the feathers may normally be less dense in some areas. The breast, for instance, normally has small areas that arent very feathered. What I see in the picture looks normal.