One of our chickens has a very swollen abdomen. She walks almost completely vertical, and looks like she's straining. She has had very watery...poops.... today, but that may be because we've been keeping her on yogurt and ACV for sour cop. When she lies down, she looks okay, but it's when she stands up that she looks like she's straining, and her bottom is very low. Please help, don't know what this is!!!