How should you triage/treat a sick chicken?

I've been fortunate as a newer chicken keeper to not have run into many issues tending my flock but after three years I have a pitiful hen who needs some tender loving care.

This is going to be my first time treating a chicken, besides treating a chick with pasty butt, and am looking for some guidance on how to general treat a sick chicken as we figure out what is the cause of her illness.

As first steps, I have separated her from the flock. She was getting roughed up by a couple of hens and was acting sluggish. I decided to bring her inside to keep her warm and I can better control the cleanliness of her surroundings. I have provided her clean drinking water, food and a diced up boiled egg to get her to eat.

Currently, she is acting lethargic and has yellow runny poops.

Thank you for any guidance you can provide.

what's worked well for my daughter's chickens is to separate the sick ones from the flock, keep there butts clean, add electrolytes, vitamins to her water, make sure plenty of fresh water to them hydrated, supplement her food with some cooked egg. peace & quiet helps too. good luck, some times they just don't make it, but give them a fighting chance

It sounds to me that you are doing the best option for the chicken.

Keep it quiet, in a peacefu7ll setting and give it food and water.

I hope things work out for you.