What's wrong with my Maran hen? -Please help!

My Marans hen hasn't laid for about 5 months. I figured it was due to the Oklahoma winter approaching a decreasing sunlight. She did molt in about December. Just a soft molt- neck feathers only. My Easter Egger went through a molt after her and just last week, the EE has been laying again.

My Black Copper Marans has a pale comb. I put in some feed today and watched the girls. The Marans was the only one who didn't go to town. She ate a bit, stopped, and then (I'm not sure if I'm describing this right) it seemed like she was trying to swollen. Her neck feathers raised a bit. She seems lethargic. I've checked for lice around her vent and didn't find anything. To be honest, I'm not exactly sure how to check for mites! I bought dewormer yesterday and just now put it in their feeder. Her poops were pretty much all white with a bit of substance in there, nothing that looked like worms. It was white and runny.

Please advise on what to do or let me know your thoughts on what might be wrong with her.

Thanks!

 

I went in the coop last night in the dark and slide a white paper towel underneath and then on top of roast. I was told if red streaks were on the towel than it is mites.

I am using vermox dewormer. It's a 1lb bag that you mix in with your regular feed.

Should I separate her from the flock?

I will try the buttermilk with scrambled eggs. Thank you.