Two weeks now...
Flopsy is a Black Star sex-linked. She turned 2 years old in April. She keeps her tail down, she has has a very dirty vent (clean now).
She had droppy eyes, she didn't lay any eggs (and maybe still hasn't after being reintroduced after a week of isolation), and she was having a hard time walking and was using her wings to keep balanced.
We had her in isolation for a week when she starting looking really bad. We did the steam bath, as well as the vasaline and vent massage to stimulate an egg passing if it was indeed a bound egg.
She was in isolation for a week, still keeps her back tail down, but was looking and sounding much better, despite not laying an egg in that week.
When we reintroduced her she found her place in the pecking order and stood her ground, which seemed good.
She is eating well and runs, but she still keeps her tail down and sometimes stays separated from the rest of the flock (7 hens in all, no rooster).
We don't give them meds, and we feed them an organic feed mixed with crushed oyster shells. They also get fresh compost (without anything that is toxic to them) that often contains cheese, yogurt, salmon, assorted greens, grains, etc.
She has been off and on like this a few times, but this last occurrence (which she still isn't fully looking recovered) is the longest and was the most disconcerting.
There have been no additions and they are kept in a large pen with a large run. Is there anything else we can
Black Stars are a Production Breed. They were developed to have about a 2 year healthy life. Some can lay over 300 eggs in one year.
Generally by age 2 they are "layed out" and their egg production organs begin to fail. From what you have described she probably has what's called "Egg Yolk Peritonitis".
This is a non contagious infection that is caused by the last of her egg follicles traveling into her abdomen instead of her oviduct.
There they are foreign material and her body attacks them, causing a retention of fluids, which expands her abdomen to the point where she first will have an unusual waddle when she walks.
As the problem progresses she has a harder and harder time getting from one place to the other.
I have heard of someone having a chicken "spayed", removing her reproductive organs to prevent this from happening again.
The fluids must be drained and a course of antibiotics is needed to kill any internal infection. This is very expensive and not frequently done.
The most common solution is to humanely put a hen in this condition out of her misery. I can only guess that this is the problem, not knowing anything more about her than what you've said.
A veterinary exam by one that knows bird species and their reproductive issues would be the only way to know for sure.
This is a very common problem for Production bred hens at this age. For chickens that live longer, but aren't necessarily as productive, I would recommend looking into Heritage breeds.
I'm so sorry this is happening to Flopsy.