Pullet died for no reason

[african chickens]

So one of my pullets who was gonna come out of quarantine today is puffed up and lethargic she also has diarrhea pls tell me this isnt anything bad . The other one looks fine.

 

[african chickens]

The other two I got with them went out a couple days ago and they seem just fine it's just snowflake

 

[HollowOfWisps]

The other two I got with them went out a couple days ago and they seem just fine it's just snowflake

Does this mean she is all alone currently? Stress from being alone can cause a chicken to go downhill quickly.

 

[african chickens]

Technically she is but as you can see in the 3rd picture her sister is right there

 

[african chickens]

I got 4 together these two were being housed together but after the other 2 older ones went out these two got separated they weren't let go because their poop was green so I separated them in order to monitor them but that has cleared up and they are right next to each other

 

[african chickens]

Unfortunately she passed away