breast feathers gone

Question
I have an flight cage with 15 finches (my strawberries just had 5 babies in January) - normally there are only 10 birds in the cage (2 blue cap cordon bleus, 2 mullicans, 1 owl, 1 lavendar and 4 strawberries). One of my adult strawberries has lost most of her feathers on her breast - this in the last week - I have removed her from the aviary and put her in a separate cage. It seems like the other female is starting to lay eggs again (she is spending a lot of time in on of the nests)
Do you have any idea what would have caused this? and what I  need to do about it?

Answer
Hi Deb,
sorry to respond so late...my computer has been down  :(
Anyways,I would think this losing feather problem could be molting...this time of year it's very normal for a hen to start her moult and become "new" again.  You could most likely put her back in the aviary with the others.
 Good luck,Elizabeth