black spots on comb, red bugs on vent?

so today i noticed that a few of my girls have black spots on the combs...and i noticed one girl acting out of sorts. i picked her up, she is pacted poop on the feathers and red bugs crawling around her vent.





what can this be?

this is a pic of the bird who is acting off with the red bugs on her vent

Hopefully this will bump your thread and an Expert will weigh in.
From the info you have given it sounds like your chicken with "red bugs" probably have red mites. There are many articles here on BYC about treatment. The Chicken Chic has an identification and treatment page:

http://www.the-chicken-chick.com/2012/08/poultry-lice-and-mites-identification.html

The problems with the combs could possibly be fowl pox or peck marks. There are also many articles about this as well. Here is one from the Chicken Chic:

http://www.the-chicken-chick.com/2015/07/fowl-pox-prevention-treatment.html

Since you have one chicken that you can visibly see the "bugs" on her, IMO I would start treatment as soon as possible for the whole flock.

Black marks are common... From being pecked... Red bugs are probably mites... That takes work to fix... There are a lot of blogs on here that give different advice but start with looking in your coop at sundown.... They like to fester in the bedding and wood!! Good luck!!!

Hi,
Sounds and looks like mites. The mites can bring the chickens immune system down and lead to other ailments.

Here is the search https://www.backyardchickens.com/newsearch?search=dusting+for+mites

We had it bad last year I put ash (from our wood burning stove) and Diatematious Earth in a big bucket and in the evening I get each chicken out and dust each one of them.
It's a 2 person job, don't be silly and think you can do it alone ( i tried). I person holds the chicken in the bucket the other dusts it. Lift the wings gently and push, the dust all over, just like the chickens do them selves.

Then you have to do the whole house. 'Casue they are living in there waiting for fresh blood every night. I used neem oil mixed with water and in a spray bottle. Clean the house and leave it empty. Take out every thing. Then I sprayed the house until it was dripping. I even found them on the doors and outside the house.

Dust the chicken clean the house, then in a week repeat. Check the chickens and the house often. When it was really bad I dusted the chickens every other day. I don't use Sevin so I wasn't worried about hurting them with chemicals.

Good luck!