Symptom list and can you name that problem? Pretty please?

Alright, so I have a 16 week old RIR pullet that has been acting funky for a few days (this is her fourth in a row, but she has been off and on, possibly even since right after I got her (I have 2 RIRs and I couldn't tell them apart at first, now I can). When she was younger I thought it was the cold at first because I had them outside at 5 weeks (they had their feathers and I live in SD, CA so not a big deal). Anyway, I had brought her in a couple of times and she perked back up. She may also be the same one that I suspected an impacted crop, which went away with some massage for a few days. I'm not positive about the earlier stuff, so that is just speculative, but I do know that it was her for the last 4 days and also a couple days non-consecutively before this.

Symptoms:
She is very slow to do anything. She generally will go along with the other chickens but stand there with her feathers a bit ruffled and neck brought in a bit.
SLIGHTLY dry looking/pale comb. I am comparing her to the other RIR on this one.
Minus a few tail feathers
The feathers around her head/neck look to be unkempt and when I was inspecting them I noticed many had just the shaft of the feather and none of the feathery-ness. I checked some other chickens and it seemed sort of similar to what they had so I'm not sure if this is normal.
Skinny, but not too much smaller than the other RIR of the same age.
Mostly pecks at food and haven't seen her eat much, I did see her eat two worms this morning out free-ranging and I saw her scratching around for other stuff.
When she walks she curls her toes in a lot more than the other chickens, and sometimes she just stands with one of her feet half way up and the toes curled in.
I have noticed a couple green poops, don't know for certain that it's her, but I would guess yes.
I'd say she preens herself a normal amount.
I haven't seen her drink, but she's probably drinking. I just wouldn't say she has increased thrist.


I checked to see if I saw mites/lice and I didn't, but I'm new so I could be wrong. I haven't seen worms in any of the poops of the birds, but I don't have her isolated (she has had symptoms for so long I know if its contagous they all are going to have it). All the other birds are FINE. I feed them organic layer, they have never been medicated or vaccinated for anything, they eat lots of bugs and free-range for at least a little bit everyday, sometimes almost all day.

Is there anything that is non-cantagious or that the others wouldn't have caught yet that fits the bill? Is there anything I can do about it? Ultimately I want production and have the chickens to save money on eggs, but I am hesitant about culling because I did get her at five weeks and spent $15 on her plus feed for the last 11 weeks. I also want MORE chickens, so it would be a shame to lose one that is almost at laying age, but obviously if she isn't going to lay or lay well it wouldn't be worth it.