There's a strong possibility of a bacterial infection. It would account for the older chickens being affected because immune systems are more vulnerable while the younger ones have stronger resistance. The cold could have further lowered resistance of the older girls. It would likely cause diarrhea.
The minute another chicken starts to show symptoms, start her on a broad spectrum antibiotic immediately. I would take a random sample of poop from the flock and have a gram stain performed to see what, if any, bacteria are present in the chickens.
Should another chicken die, refrigerate the body immediately and locate an agricultural lab to do a necropsy so you can identify what has been killing your flock.
Just is case it's bacteria that is responsible for these deaths, extreme care should be taken to wash your hands, cook any eggs thoroughly (no over easy fried eggs) since bacteria sickening poultry can also sicken humans. (Example: salmonella.)
The minute another chicken starts to show symptoms, start her on a broad spectrum antibiotic immediately. I would take a random sample of poop from the flock and have a gram stain performed to see what, if any, bacteria are present in the chickens.
Should another chicken die, refrigerate the body immediately and locate an agricultural lab to do a necropsy so you can identify what has been killing your flock.
Just is case it's bacteria that is responsible for these deaths, extreme care should be taken to wash your hands, cook any eggs thoroughly (no over easy fried eggs) since bacteria sickening poultry can also sicken humans. (Example: salmonella.)
