Hen with runny poop not laying; otherwise acting healthy

[FiveChickens]

I have a hen who is between 1-2 years of age. At the beginning of the summer she went through a molt, but has since grown most (if not all) of her feathers back nicely. She has very runny poop and now has a "messy bottom." I need to bathe her about twice a week, as I don't want her to get an infection. When I pick her up with both hands on her sides, the runny poop comes right out of her! When she does have a solid poop, it is very tiny. Seems as though she is blocked. She stopped laying for awhile, and I believe I was getting an egg from her very sporadically a few weeks ago, and one a few weeks before that. I know this because two of my other white hens lay almost daily. She eats, drinks, dust bathes and free ranges around the backyard normally. I have four chickens in total and the other three chickens are healthy. I always keep a very clean coop and run (I scoop poop from the coop and run daily, change nesting box bedding every 1-2 weeks, change the water every two days). I haven't noticed any worms in the poop, but is this what it sounds like?

Note: I dealt with mites about a month ago thanks to a very wet beginning of summer, but haven't seen any since.

 

[Eggcessive]

In hot weather runny stools can be common if they are drinking a lot of water. Adding a probiotic to the water (many are available now in the feed, or with vitamin/electrolyte mixes) or a small amount of buttermilk or plain cultured yogurt may help her diarrhea. Trim all of her messy feathers, and keep the droppings off to prevent flies and maggots. In hens her age, you can sometimes have internal laying, egg yolk peritonitis, or another sort of reproductive problem, causing diarrhea, yolk in droppings, shell-less eggs, or a reduction of laying. Here is some info on that:
http://scoopfromthecoop.nutrenaworld.com/tag/laying-issues/
http://www.chickenvet.co.uk/health-and-common-diseases/egg-laying-issues/index.aspx

Vent gleet happens sometimes, but usually there are bare vents with white or yellow patches seen around the vent. Here is some info about that:
https://www.backyardchickens.com/a/vent-gleet-aka-nasty-chicken-butt
http://www.tillysnest.com/2012/12/vent-gleet-prevention-and-treatment.html

 

[FiveChickens]

Thanks for the suggestions.