Hello, welcome to the forum .
As your female budgie is now an adult. When her cere gets brien and crusty she is in breeding season.
" Females with a tan cere may develop brown hypertrophy of the cere, a thickening of cere tissue. This occurs from hormonal activity and is not dangerous nor does it need to be removed. Normally, the flaking hypertrophied tissue sloughs off over time and only becomes of concern if the tissue occludes (closes off) the openings to the nares."
During breeding season they will sometimes pull out feathers to line their nest . Even without a nest available she may be practicing.
But mites are also a concern. The scaly keg mite makes legs and around the nose thick and crusty and they will lose feathers on tgeir face.
But I think you have breeding behavior. If yiu are not planning on breeding, font provide a nest. If she lays eggs anyway you can boil them and give them back for her to sit on. Because if they don't have eggs to fit on they can keep making new eggs and get in trouble or die.
Just stuff to think about ahead if time since you have a boy and a girl ..