Check them for lice. I lost a bunch of birds to them, totally sucked. If you've never had to deal with lice before look near the vent and around and under the wings. It is unlikely that you'll get to see the litle bugs but you should be able to find their nests. The nests look like little...
I have 3 adult partridge chochin hens and 1 partridge rooster. All are under a year old, the hens are proven layers. I'm in NY but I am willing to ship.