Her body size isn’t much larger than the other girls but she’s way heavier than any of the other girls. I just left to go out of town for 3 days and don’t have polyaid. I have been taking pictures of her poop the last few days. She seems like she really wants to poop but only has little poops. They are little normal consist poops not watery. She’s eating well and drinking which is good. Her crop was full this morning after I gave her dewormer and a little scratch. Normally whenever I touch her or go by her she squats but has not for about a week.It wouldn't be something like necrotic enteritis then, that scars the digestive tract and the lose weight very quickly.
When you say large, do you mean overall body size, or us she heavier than the other girls? One thing that comes to mind is acites - water belly. If her abdomen is big/dense, it could be that. They can fill up with water to the point that it starts pressing on their organs and making it difficult for them to breathe.
Do you have any rescue remedies on hand? Polyaid or similar?
You may want to isolate her in a temp-controlled environment and monitor how much she's eating, how much she's drinking and what her poos are looking like - (color and consistency for both the whites and solids). Putting her down on an old towel with paper towels over top should allow you to get a good look at them.
If she's off her feed, try offering treats she's familiar with or some hard-boiled egg to see if she's interested.
Have you checked her crop? Empty in morning, full at night and usually has at least something in there throughout the day.
When you checked her abdomen, did she brace like she was being mounted?