What's wrong with my hen

[WolF111]

That looks like vent gleet damage.
I had a hen that had unnoticed vent gleet that caused similar damage, but not as bad.
While also treating for the vent gleet to get her digestive system rebalanced, I started working on her to remove all the hard crusty tissue that resulted from it. It took daily soakings and careful picking of the chunks to get them off. This was in late winter so I had to stop the soakings on the bitter cold days.
I worked on her for over a month and made good progress but in the end I didn't make it in time as her vent lost it's elasticity and she was not able to pass her eggs when she started trying to lay again in the spring.
After removing a third egg from her in 6 days as she then started to struggle to poop as well, I conceded that the best option for this hen was euthanization.

So sad to hear about your hen. Mine is doing really well with the treatment. She's passing normal stool now and I'm very near to get all the dead tissue off her. She's showing all normal signs and no signs of sickness whatsoever. I will continue the treatment till she completely recovers.