1. did you buy her as a chick? If not the move may have been traumatic. Chickens do not like change. Even the removal of one bird can throw off the hierarchy and be upsetting. Also a sudden change in feed can be traumatic too. A gradual change from one feed to another is best. I usually mix grower and layer for a while.
2. is she the only one in the flock? single breeds of birds in a flock don't always work out well. Though I do have a couple of birds who "chose" to go in with my Dels. and Orps. They went in on their own so I just left them with the flock of their choosing. I really think they are more affected by color than breed though.
3. I believe Nature Berry is a retail store and doesn't breed their own birds. If they've hatched eggs they purchase there is not telling how healthy the breeder birds are or how closely they are related. Unfortunately the term "breeder" is loosely used. There are many "chicken mills" out there.
4. If you see not discharges from nose, beak or vent then most likely it's an internal problem that you or a vet could not solve. Chickens do develop kidney, heart and other genetic problems. They also can get cancers.
5. I personally did not get Polish because of what I've read. All chickens do not have the same personality disposition. New chicken folks sometimes just pick out breeds that look pretty, not realizing some are hyper, others calm, some are bossy and flighty. I personally like Leghorns but they are easily spooked.
Delaware, Orpington, Wyandottes, Sussex and others are calmer and more people friendly. Leghorns, Dominique and some Barred Rocks are not. There is of course exceptions to every rule.
I wish you well with your girl, but please do not lose heart. Chickens are very therapeutic. Many of us have learned through trial and error.
Rancher
Silkies too are friendly but I didn't mention them as they are not real chickens. (they are aliens from another planet)
