One of my budgies, Fae, has super short and slightly frayed tail feathers. She had normal sized, but frayed tail feathers when I got her a few months ago and I thought it was from rubbing against the cage. Since then the feathers got more and more damaged (I am unsure how) until one day I noticed the long damaged feathers were out of her tail. The short feathers left are still looking frayed and it makes me very sad! She gets along with the other two with her and I haven't seen any fighting between any of them. She likes to walk around on the bottom of the cage with the others and her tail drags, but so do the others. Same as sitting on the side of the cage. Is she plucking them or is something wrong? When she did see a vet after I got her she said she was healthy (as with the other two). Have the feathers just not grown back in yet? How long does that usually take? (She is the white a turquoise blue one. She is next to the others to show the tail size comparison.)
It's possible that her tail feathers were worn from climbing around in the cage, even before you got her (she looks to be ~5 months) and those feathers are now beginning to drop due to her baby molt where all of her feathers are eventually molted, including tail feathers. The long tail feathers once molted will be replaced by her adult tail feathers which are starting to grow now, which seems to be what is happening. Feathers don't grow until the old feathers are lost. Most of these longer feathers grow back in about two weeks. Any new tail feathers found when you clean the cage could be noted and once lost, will be replaced. If you find blood feathers on the cage floor, this would indicate there may be problem. Otherwise I'd wait and see, for a longer beautiful tail.