Hi my chicken have the same symptoms.!!!!!
what can I do ??
Like 2 days ago she has this symptoms. Yesterday she was fine. Today she dont eat, dont drink, dont move drom a single spot and her poop is yellow :(
I am not an expert by no means but my chicken (black austrolorp) suffered from this. I did manage to save her by giving her apple cider vinegar in the waterer and giving her Ultra kibble. Ultrakibble is known to firm up the poops so I gave it to my hen. Also I know chickens should be eating their feed but when my was down I fed her anything she would try to eat. bread, mealworms anything to just keep her going. It's not a perfect solution but I just tried to treat the symptoms and did my best to care for her. It has been two months ago and although she is not laying as well as her sisters she is alive and does not suffer from the issue any longer.
Best to start by bring her inside where it's warm. Sick bird are almost always hypothermic (too cold), so get her inside ASAP! Ideal temp for a sick bird is 80-85 degrees.