I have a chicken that is being really slugglish, Help?

[Kk chickens]

My 3 year old long horn chicken started acting very strange. First she started refusing to speak but acted normal other wise. Then she started sitting down for long periods of time, showing no activeness what so ever, still never made a sound, and started refusing to eat. We brought her inside gave her some VetRx and another antibiotic just in case it's a respiratory issue cause of the humidity we are experiencing. When she was sleeping she laid down with her head on the floor as if she passed out. In the morning I checked her and her crop was full and squishy. Well today she is still really sluggish and just stays standing up. She has not sat down at all. She has been drinking water and barely eating. Her poops have been very watery and green. She is also a little bit swollen from the back. I also checked her breath and it's normal. What could possibly be wrong with her, and what should I do to help her?