Update as of 11-17-23: We had to move this bird to true solitary confinement with no possibility of interacting with her flockmates because she was pulling at her flockmates' feathers through the bars and showing no signs of improvement. Not only this, but one of our other babies has started...
As it says on the tin, but here are more details regarding the issue.
So I got 5 baby birds (now around 16 weeks old) from a fairly reputable breeder a few months ago to go along with my three other adult birds. Everything was relatively normal as far as flock integration goes. The babies were...