Weird black spot on swelling on rear end

[Snicketysnoksnaksnik]

Her lower belly looks very full and enlarged as though she might have ascites. Tumors or liver disease from egg yolk peritonitis, as well as heart disease can cause ascites. The wound under her vent looks like pecking, but in warm weather, flystrike (maggot infestation) can occur there. I would try to make sure there are no maggots. Chlorhexidene 2% spray or Vetericyn can be used to clean the wound twice daily followed by plain Neosporin or Triple Antibiotic Ointment.

It is very warm currently so I’ll check for maggots. I’ll also check to see if I have any of the items you suggested.

Can you get a photo of her vent?

The black almost looks like dried on cecal poop, but it may be a large scab.
I would apply an ointment or oil to the black portion, especially around the edges. See if it starts to work loose over time revealing healthy skin. I don't think I would pick it off, but it may lift over the course of several days if you apply the ointment/oil daily.

I agree, the abdomen looks like it's full.

For me, if a hen is able to move about, still roost, isn't getting pinned down and picked on by the others, then I leave them with the flock. I let her decide about her roosting place. Sometimes once they start having reproductive issues, they start roosting lower and lower until they are unable to roost, then they choose a comfy corner. Once they start sleeping in a corner, then I make sure they have adequate clean bedding for overnight.

I’ll try get a photo soon. Yesterday I applied an ointment to it, I’ll make sure to do it again today.
She’s always stayed on the lowest roosts even when she was fine because she has a problem jumping. Although recently she hasn’t been going on the roosts whatsoever, so instead of putting her up I got her a crate with bedding.

 

[Snicketysnoksnaksnik]

I couldn’t get a photo since I’ve been a bit busy. She’s getting dirty again so I cleaned her. She’s no longer with her flock instead she‘s with my meat chickens. She has a full crop and is drinking quite a lot, she’s a bit drowsy still but not as bad as before.

 

[Wyorp Rock]

I couldn’t get a photo since I’ve been a bit busy. She’s getting dirty again so I cleaned her. She’s no longer with her flock instead she‘s with my meat chickens. She has a full crop and is drinking quite a lot, she’s a bit drowsy still but not as bad as before.

Drinking a lot and her crop being full, I would re-check the crop first thing in the morning before she eats/drinks. If it's not empty, then I would begin treating according to the article linked.
A lot of times when a crop is not emptying, there's something else going on like a reproductive issue as suggested by @Eggcessive in the previous post.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/

Her lower belly looks very full and enlarged as though she might have ascites. Tumors or liver disease from egg yolk peritonitis, as well as heart disease can cause ascites. The wound under her vent looks like pecking, but in warm weather, flystrike (maggot infestation) can occur there. I would try to make sure there are no maggots. Chlorhexidene 2% spray or Vetericyn can be used to clean the wound twice daily followed by plain Neosporin or Triple Antibiotic Ointment.

 

[Snicketysnoksnaksnik]

Drinking a lot and her crop being full, I would re-check the crop first thing in the morning before she eats/drinks. If it's not empty, then I would begin treating according to the article linked.
A lot of times when a crop is not emptying, there's something else going on like a reproductive issue as suggested by @Eggcessive in the previous post.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/

I’ve been checking her every morning and her crop is always empty, when I shut my chickens I always smell the breath of all my chickens since I’ve dealt with sour crop before. Her breath doesn’t smell bad, to me it smells the same.
I forgot to put on oil today but I’ll make sure to do it tomorrow

 

[Snicketysnoksnaksnik]

I checked her this morning and she isn’t doing too well. Her crop is empty but she is falling asleep and uninterested in food and water. I moved her into a cage with fresh food and water. Currently she’s just asleep in the cage so I’ll check on her later with some fruit that she usually eats quite fast

 

[Snicketysnoksnaksnik]

It started raining heavily so I covered up her cage, then it got windy so I covered up the sides also. The side cover must’ve blown off, when it stopped and I went to check on her and she was soaked and flies covered her. She was quite cold and unresponsive, she seemed half-dead. She looked terrible so I decided that it was wrong to keep her alive. She looked as if she was in pain. She was just killed, I feel sorry that that happened to her.
I disinfected the cage, cleaned her food and water bowl and moved the cage.

 

[Wyorp Rock]

It started raining heavily so I covered up her cage, then it got windy so I covered up the sides also. The side cover must’ve blown off, when it stopped and I went to check on her and she was soaked and flies covered her. She was quite cold and unresponsive, she seemed half-dead. She looked terrible so I decided that it was wrong to keep her alive. She looked as if she was in pain. She was just killed, I feel sorry that that happened to her.
I disinfected the cage, cleaned her food and water bowl and moved the cage.

I'm sorry about your hen

 

[Caro2]

Hi. I just posted an update on my chook who had this. It looks like an Eschar. It is dead tissue that forms a wet or dry (like yours) seal over the wound. It will not heal no much how you clean it. If you google Eschar you can see the treatments. I am not a vet so I won't recommend anything but I chose to surgically remove it on my chook. Three days, healed over.

 

[Eggcessive]

So sorry for your loss.