I have a new coop, and 12 chickens ranging from 4 to 8 weeks old. 6 of the chickens that are in there we hatched out from eggs, they are the 8 week old chickens. The remaining chickens are a combination of others we had hatched, and a few we had bought at a flea market. Yes, this is where the problem comes into play. We have had 2 chickens who had previously seemed fine, start to stagger around, and eventually loose all movement in their legs, eventually dying. These were some of the flea market chickens, but we've also lost one of the 8 week old chickens (we suspect it was the same thing, but we were on vacation and did not see the symptoms ourselves). We suspect mareks disease. My question now is, what can we do about the remaining chickens? They all share the coop, an area about 7 x 6 ft. Will they all come down with mareks now that they have been with the infected chickens? Will vaccinating them now do any good?