Strange observation...what does this mean???

[Certified Chicken Lover]

It all started a few days ago when I noticed my Ideal 236 was starting to get a poopy butt. I brought her in yesterday to bathe her as it seemed to be getting worse, but as I was drying her I noticed something strange, her vent seemed to have largely shrunk. I tried to take a picture but you really can't tell from the pics how small it is. Why and how has this happened? I'm assuming this may be one of the reasons she started getting a poopy butt, but I don't know for sure. Is there something I need to do to prevent it from further shrinking? This is all so strange to me and I can't find anything online explaining causes so I would really appreciate your help!

Important info:
Diet: Purina Layer Crumbles
Age: 3+ (she will be four in May)

Other: she doesn't lay and hasn't for months. She has water belly and we have been draining her around every month since August 2023. She acts normally otherwise, she has been eating and drinking normally. I know her time is limited, so we are just trying to help her stay the happiest with the time she has left.

Please don't rely too much on the image because in person you can really tell how small it is, and I know it has shrunken.

 

[Tookie]

Her vent looks smaller because her abdomen gets distended from the water belly, I've had hens with water belly and their vents looked like that. Her vent kind of stretches out in way causing that, if that makes sense.
She's getting a messing bottom also because of the water belly that's causing her abdomen to be distended, therefore its harder for her to be clean.

 

[Certified Chicken Lover]

Okay that makes sense. Thanks so much for your help!