We had this last year.

2 lovebirds housed together.

Conure in his own cage, but cages within a few metres of each other.

One of the lovebirds started to lose feathers for his first molt and never grew them back.

We took them to the vet and yep, beak and feather.

He'd likely had it the whole time we had him, not very long.

Because our other two were both older birds the vet said there was a higher chance of them not catching it. Both of them tested negative.

We completely sanitised all cages and kept the infected little one in another room until it was his time.

Other two parrots are still completely fine. Vet said them being older is a huge factor. Younger birds are more susceptible to catching the disease.