I had never heard the term keel before.How many are in the "sick pen"? Have you felt the breast (keel) of all the birds in that pen? I'd be willing to bet money that the worms you found came from the thinnest of them. Does that better sense (haven't had my coffee yet)?
-Kathy
The main coop is down to 11 hens and two roosters. It may be the Lavender roo. He sits there a lot, and when the vet came to draw blood I noticed that he had lost a bunch of weight, but I chalked it up to him having been so sick. He presented first and is still not fully normal.