Question. I have bought crested cream leg bars from 3 diffrent people. I had one who was suposted to already be laying die on me within two weeks and mever laid an egg. The guy i got her from was like sorry. I often enjoy lighting $80 on fire. He didnt even offer me a partial refund or a replacement bird. I got a second one I got january 9th. She was about 3 months old. Today i went up she too was suddenly dead. She did have the funny dark colored poo stuck to her bottom like she had just went potty and died. It hasnt been cold latly here in cali. Only in the 50s at night. I do have a roo and female chicks that are babies there Are from a december hatch from another person. They are doing good. What would cause them to just up and die? Are they not as hearty of a burd or what? Now when my roo is older i have to find an adult one. I wanted to try my hand at breeding but nothing grand scale. For me to keep and to give some to my friend who is starting her own flock soonish.
Since you live in California, you can get a free necropsy from http://cahfs.ucdavis.edu/
If there is a lab close enough you can take the bird in. If not, call them and get information on shipping--see if they still let you use the UCD discounted Fedex account.
It is the best way to see what is going in. It is common for new birds to not be resistant to something at your place, like a lethal to some type of mareks.