male plucks female head feathers

[mano]

Hi all. Good forum here. Many thanks to the moderators.
I have recently purchased a 2 year old pair of breeding parrotlets with in the lst couple of weeks. I dont have much experience with them and they seem to love and cuddle each other but...... I got up the other day and checked on them and the female was totally bald just on her head. The people I purchased them from wont answer my questions except to say that when the pair decide to mate they pluck feathers to line the nest. It doesnt seem to bother the female and was rexcommended using Bitter Apple on her to stop the plucking.
Any help out there?