New chickens are sick, what to do?

[marycorbin]

I was given two silkie hens two days ago and they are sick. Bubbly eyes, congestion, one is sneezing... they stank when I first got them, but they also had mites and since I treated those and they are in a cleaner pen, they don't smell bad anymore. They are currently housed in a temporary coop on the other side of the yard (at least 40 feet from each other) from the two hens I already had, but it is possible/likely they came NEAR each other when my hens broke out yesterday.

I've read some truly awful scenarios about these symptoms.
My question: should I cull my new girls before they infect my old girls (this would be really sad for me and my kids)? Should I treat and just wait? I read that it could be something really bad that would require me to treat and retreat the entire flock monthly! Are they far enough away, or is that irrelevant since they may have had contact yesterday?
What to do, what to do?

 

[marycorbin]

Also, how long should I wait to confirm that my old hens are in the clear? I have chicks in the house, and I don't want to expose them unneccesarily.