I have 3 chickens that are free ranging, the eldest has not been herself for a few months now, I put it down to her getting old (she’s 6) however about a month ago I noticed she was having loose stools and walking very slowly. She isn’t egg bound but the eggs she is laying are very dirty. About 3 weeks ago I noticed a dark patch on her beak, at first I thought it was mud but it’s now spread quite rapidly., she is very lethargic and her stools are really runny and she is spending a lot of time laying down. I have tried all the local vets and none have anyone that deals with exotic pets ( I didn’t know a chicken was classed as exotic) but they will help for euthanasia! Does anyone have any idea what could be wrong?