Silkie chicken with tail down. poopy vent, but still eating

[Pdx Matt]

We have a less than 1 year old Silkie hen, and we just noticed this morning that her tail is pointing downwards. She is still eating and moving around, but she looks a little scrawnier than usual as well. We picked her up to look at her vent, and it's poopy although it doesn't appear to be pasted shut.
We are newbies to chicken keeping and are not sure what to do for her!
Any advice?

 

[Pdx Matt]

Brought her inside under a light. We'll see how it goes. We're giving her water with a couple drops of apple cider vinegar. In the morning, planning to give her some mash with her food, a little yogurt, garlic, and raw honey. We'll keep her confined and monitor her.