3 week old chick with swollen feet and peck injuries

I posted yesterday about reintegrating the chick, but today she seems much worse, so I think it's more than just she got pecked. I think there is some kind of disease process going on.

1) What type of bird , age and weight. Not sure on weight, but she is 3 weeks old and very tiny compared to the other 26 we got at the same time. She is a Barred Rock from McMurray May 30. I would say she isn't even doubled in size from when we got them. She feels bony where the others are filing out.
2) What is the behavior, exactly. She is lethargic, fluffed, and peeping very sadly. She doesn't move around much at all, and tries to crawl under the other chick and hide. She is scratching at her face/beak a lot and preening her legs a lot which is basically her only movement. Though she does come over to food when you put something new in. She seems to also be having some difficulty breathing as I can see 'puffing' out by her beak when she breathes so I think it's pretty labored.
3) How long has the bird been exhibiting symptoms? This is day 4. Her feet look a little worse today--swollen. Photos attached.
4) Is there any bleeding, injury, broken bones or other sign of trauma. She initially had peck injuries (I thought??) on her chest/head/comb/feet, but now I am wondering if it's something else. Mites? Disease of some sort? And her feet actually don't look normal compared to other chicks, the rear toe doesn't touch the ground. Not sure if it's due to whatever process is going on, or if it's deformed.
5) What happened, if anything that you know of, that may have caused the situation. I think she was pecked, but now not sure. All other chicks are totally fine.
6) What has the bird been eating and drinking, if at all. She seems to be eating and drinking but not vigorously like the rest of the chicks
7) How does the poop look? Normal? Bloody? Runny? etc. Normal stools.
8) What has been the treatment you have administered so far? Separated her and the next smallest chick into a separate enclosure.
9 ) What is your intent as far as treatment? For example, do you want to treat completely yourself, or do you need help in stabilizing the bird til you can get to a vet? I would like to treat here and can run (60 mi round trip) to feed store to pick up what is needed, but would like to make just one trip if possible!
10) If you have a picture of the wound or condition, please post it. It may help.
11) Describe the housing/bedding in use Straw on bottom with pine shavings on top. In her separate enclosure, just pine shavings.





Beak has some marks by it.


Compared to next size of the same breed. She is just tiny, and these two are the smallest. The others are probably 2x or more the size of the sick one.

 

Bumping.

I need to leave within the hour if I'm going to make the feed store. Was hoping to get ideas though will check with store for sugeestions if I don't get any here.

Thanks all