My chicken flock began with a hand-me-down flock of older laying hens my neighbor gave me. If I could do it all over again I would definitely start differently but, if nothing else, it has given me ample opportunities to learn about chicken husbandry. We lost one of those gals a few months after getting her. She had chronic diarrhea from day one and I tried buttermilk and epsom salts but had zero results. Another one of those old gals got sick within the first six months and died - just becoming lethargic and dying within a couple days of me noticing her change in behavior. After having those older hens for a few months I got some chickens from a local lady getting rid of her flock. Again, I would not do this again but you live and learn. They were healthy for the most part with the exception of one I have named "poop butt" who also has chronic diarrhea, crappy feathers and does not lay eggs (but is otherwise happy seeming). OK, so maybe a year ago we lost another of those older chickens. She looked like maybe she had gape worms - opening her mouth and yawning then started looking a little sick. I was literally heading out the door to pick up some antibiotics for her when she coughed up a tumor. I took her to the vet and had her euthanized (too much of a softy to do it myself). The vet said since she was older she likely had cancer. A few months later one of my second-addition chickens suddenly became lethargic, with diarrhea, and died within the week. She was not old, maybe a year old. Since then I have lost one more of the old hens. She always has been elderly - she is on the perch at about 3pm every day. She has never laid an egg since having her. And she has started looking scruffier and scruffier these past few months. She got a very poopy butt this last week, started getting weak, and then I found her in the corner of the run, dead. So, that is part 1. Part 2 is that we have some chicks we got this past spring. My girlfriend worked at a feed store and we ended up with a bunch of the "un-sellables" (mostly gold sex links). When they were old enough to defend themselves we added them into the main flock. However, about two months in I noticed one walking awkwardly, like she had no balance. I removed her and within a few days she was splay-legged and not walking at all. That was about 6 weeks ago. Since, I have kept her isolated. She is a yard bird now and sleeps in our garage. She regained her ability to walk but her balance and coordination have always been off and it seems to come and go. She wobbles around some days barely maintaining balance and others she will sprint across the yard (ugly but effective). Now I have a flock of about 30 hens. Half are young (3-6 months old). Maybe a quarter are middle aged and the other chunk are elderly. I wormed them in the spring and plan on worming them again this fall. I found a bunch of lice this summer and dusted for it. I have been working on getting them as healthy as possible - increasing their run to a size big enough for them to forage much of their own food and clean themselves with dust baths. It's all been trial and error so far (mostly error) but I am working towards having as healthy and natural a flock as I can. I'd eventually like to be producing their food here and free-ranging them primarily. Here is what I am thinking I am dealing with: Option 1 - mixed bag of old hens that are dying of various diseases/old chicken age. Could be cancer, could be some other sickness. Getting them at unknown ages from a couple different farms is a great way to end up with random diseased chickens. I figure I need to adjust their diet to help the one with the chronic diarrhea. But the flock now is healthy looking, active, laying, etc. Option 2 - somewhere along the line I got a Marek's chicken. The isolated bird now is the only one who would be exhibiting symptoms but all would have been exposed. I would assume the tumor chicken actually had Marek's and not cancer as the vet had suggested. No one else has shown any symptoms (paralysis or weird gates) other than the ones. I am trying to sort this all out because A) I don't know what to do with my yard bird. I'd like to put her back with the chickens but do not want them to get whatever thing she has going on. B) I want to get the one with the poop butt sorted out because I have been using her as a gauge for the general health of my hens (if I can get her healthy I figure I am doing great) and C) I have two hens sitting on a few eggs apiece right now. I don't want to keep adding chickens if there is Marek's in my flock. My plan is - vaccinate all chickens and the new chicks for Marek's (I know it is not very effective in older chickens but I only have 30 and the dose is for 1000 so why not) - get a necropsy on the next chicken that dies. I should have done this already but still learning... - keep working on getting chickens as healthy as possible (diet, free ranging, etc) - keep my yard bird isolated until I have a better idea of what is affecting her I know there are folks with a lot of knowledge on this site so any advice is appreciated. I am just starting to connect the dots here. And, just in case it comes up, I am not open to the idea of culling the whole flock, even if Marek's is present. I would rather learn to humanely kill them if need be but I don't want to do any "preventative maintenance". I am attached to a few of those gals and can't do a re-start that easily. Sorry for the novel but I am just trying to piece together if these deaths are connected or just simply the result of older/unhealthy birds. And, the timeline for this is over the past year I would say. Thank you!