Dear chicken friend, were these chicks vaccinated against Marek's?
I could be wrong and apologize for cutting to the point, probably shouldn't even say it.. and HOPE I'm wrong.

Looks like wry tail and retarded growth essentially.. caused by Marek's disease virus. Please don't jump to this conclusion but do be aware that it could be one of the MILD symptoms.
Marek's Virus FAQ
COULD be genetic weakness since it's only one! Easter Eggers have always been fairly hardy in my experience but they can't all get the good genes. One of my favorite birds and she is lovely too!
How long has her tail been down? Did you ever need to treat for coccidiosis? What is their standard feed routine including treats and supplements.. I mean at the bottom of the pecking order, surely she isn't getting excess treats?? Is she getting enough nutrition still?
Just looking for clues.
Hope you get some answers & she recovers quickly!
Thank you for responding! I found her outside later this afternoon with three other chickens and her tail had come up. (see post for details) So, I feel a bit silly but you never know with chickens.. However, in response to some of your questions I thought I would still answer them to make sure I am on track with my flock.
I did not vaccinate them for Marek’s. She came from
Tractor Supply and at the time I misunderstood about hatchery vaccinations. I’ve read they should be vaccinated early and will do so with any others I bring in. They have not had coccidiosis. The only thing really off that has happened is several chickens had really loose poop a few nights ago which I was able to link to a neighbor putting a variety of really greasy scraps and pineapple leaves over the fence for them. I cleaned up what was left on the ground and they were fine within a day.
I have thirty-one chickens. I am feeding the flock Dumor 16% Layer pellets but am considering going to flock raiser because of the roosters and supplementing with oyster shells. (Thoughts on this?) I used to feed crumble but the last two bags were nothing but dust and not usable.
Along with the pullet that is under discussion I have a rooster that was from my original flock that stays on the roost a lot. He survived the fox attack and is at present being taught his place by the older rooster. I installed food and water dishes on the wall above the roost where I feed both of them after I realized my rooster had been without food and water for almost an entire day. When I do treat feed I usually hand feed both of them.
On Fridays I usually toss in a butternut squash or something similar. It is dense and gives the chickens something to entertain them for about 3 days. The rest of the week I dispense treats based on the weather. If they are stuck inside I give them 2 treat balls with dried meal worms inside. They love to peck them around the coop. Other treats include apple, cranberries, blueberries, carrots, and an occasional cabbage. Instead of a fruit or veggie I occasionally give them a little bit of 6 grain scratch grain. I try to make sure that their treats do not exceed 10% of their daily diet and always wait to treat feed until later in the day. If it is going to be very cold at night I give them a little scratch grain before they roost but only enough for a few bites per chicken. On days when it is nice outside I do not give a lot of treats. My EE’s are grazers and all of them enjoy foraging.
I add AC vinegar with the mother 1 day a week to their water, 1 day I add a vitamin/electrolyte mix to it. On bitterly cold days when they are stuck inside I put just a few drops of VetRX in the water.
As far as hygiene, their waterers are cleaned and filled fresh daily. Every morning I scrape down and mop the poop board and roosts. If there are any large noticeable piles of poo on the floor I remove them as well. The coop is bedded with a substrate of pine pellets with a layer of flaked pine over them. This controls the moisture pretty well. We shoveled out and cleaned the whole coop after 3 weeks because they were in so much due to weather. The girls are really clean with their nesting boxes, but I do freshen them up every few days, adding bedding. While I am in the coop I try to take turns checking a few chickens each day looking for anything suspect. I also check their poop for any visible parasites.
That’s about it. I am still learning. Part of my childhood was spent living across from a commercial poultry farm that my dad worked at. We occasionally had chickens at home but having these has definitely been a learning experience and I am eager to learn all that I can...so any insight you can offer is appreciated.

I love my chickens.
Thank you again so much! I will continue to watch her. She is one of my favorites…such an odd little girl.