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Do you have more info or photos of your hen you wish to share? The OP has not been active since last year, so they may not respond.
Photos and symptoms that you see may be helpful.
Do you have any photos of her and her poop?
When is the last time she laid an egg?
At 6 years of age, she may be having some reproductive issues or her age is catching up to her.
Feel her abdomen below the vet between her legs for bloat/swelling or feeling of fluid.
I would get some poultry...