fluid sack is somthing wrong?

[Richie704]

My cornish hen has a large fluid sack on her left side. She is 3.5 months old. Seems abnormal to me. She seems lethargic most of the time and her speech seems to be effected. When I let them out to roam, she often just lays down. Upon inspection of her belly, it seems unhealthy, irritated etc. I thought about draining it. Thoughts?