Bugs?

[A & H]

Recently one of my hens got mites or something. It was very queer because i dusted her with diotomaceous earth and bathed her repeatedly without any effect, but the other two didn't get it at all. She started having a messy vent area. She didnt lay at all, I think, from when she got it. I noticed it one morning when I was cleaning out the coop, there were tiny grey bugs crawling up my arms and legs! she got worse and worse, nothing I tried worked. Her comb turned pale and purple. My hens usually sleep in the summer on a little flat roof in the run, but one night she was in the nesting box and didn't respond at all like normal. I put her on top of the coop and ran to get a flashlight, when I came back she had fallen off! I shined the light on her bum...It was terrible and I caught a glimpse of what looked like blood. She was NOT acting normal and I couldn't stand it and i knew she was in pain so I let one of my family put her down. I felt terrible, but fortunately my others didn't get it. What kind of mites do you think got her? What should i do if they come back?

 

[Wezdin]

DE will not kill mites, You need to use something like permetherin.
you can find it at any feed store. Do a thorough clean of the coop and roosts to get rid of any others.

 

[Eggcessive]

Permethrin garden dust or spray is very good to use for chicken and coop treatments. Here are a couple of food articles about the different types of lice and mites, and what to use to control them:
https://anrcatalog.ucanr.edu/pdf/8162.pdf
https://the-chicken-chick.com/poultry-lice-and-mites-identification/