I have a couple of months that one or two chickens die on me. They are OK and suddenly die over night. My flock has grown and now I have polish that I don't want to loose. The thing is that I have been complaining about two roosters that comes from a neighbor but can't get them away. My flock don't free range but I still feel that they should be kept away. The thing is that today I saw one laying around and when I checked him it has running nose. So time to worry. What can I do to prevent more deaths. I know I have a problem. Just not how big