My finch seems to have lost all of the longer feathers from one wing?

My female fire finch is sitting on the floor. Upon closer examination, she is missing most of the longer feathers on one wing. she can fly, but not far and not high. Otherwise, she seems fine. No feathers missing elsewhere, not in any quantity,anyway. I can see the longer wing feathers tered on the bottom of the cage. She is not puffed up or sickly looking. Legs are fine and the feet as well. After I picked her up to examine her, then let her loose on the cage floor she fluttered upwards and clung to the cage bars for a short time, then settled back onto the floor. Is this a normal molt, or is this a problem? The pair get along well, sit next to each other, etc. The male will sometimes sit on the cage floor next to the female. But a couple of weeks ago I did see the male pull a feather from the female and drop it to the floor. I never saw that behavior again, though, and I do check them often and watch them for periods during the day. The male is not aggressive.