6 year old hen acting lethargic

[Snicketysnoksnaksnik]

Hello
I have a hen who is roughly six years old, she has been acting off for a week or so now.
-she’s seemed scruffy
-vent area is dirty while in the past it has been very clean
-comb and wattles have been pale but then reddened again (currently a pale-ish red)
-has been much lower on the roosts and she is a top hen

today i found her on her own in a little secluded spot, at first i thought she was okay and just resting but she didn’t move as i got closer. she is normally quite skittish so i found it odd. i went to pick her up and she is very skinny.

i’ve taken her and put her in a crate and am now giving her tomato, lettuce, wet feed and some electrolytes. she‘s eating quite well but keeps dropping off to sleep.

any ideas what this might be?

extra things about her:
-she’s a small mix-breed bantam
-we hatched her six years ago
-she hasn’t laid an egg in around two years

 

[Snicketysnoksnaksnik]

I’ve just given her a shot of a wide-range antibiotic incase it is a disease of sorts

 

[Snicketysnoksnaksnik]

Did a quick check and she does not seem to have any external injuries or parasites/maggots.

She shouldn't have worms since we have dewormed the flock in the past but would it be best to do another round?

 

[Snicketysnoksnaksnik]

She's still alive, I put her outside in a cage during the afternoon with food and water. She will be sleeping in a crate separate from the others.

She seems to be a bit more alert but overall very off

 

[Snicketysnoksnaksnik]

She unfortunately passed away last night. I decided to put her in the coop in her own crate so she could be with everyone a last time
I don’t think it was a sickness, I‘m starting to believe it may have just been her getting old