2 week old and 4 week old Plymouth rock chicks

[BLT1]

Hi I'm new to the website and owning chickens. I do have experience with birds and animals, on my own and as a biologist park ranger.
I have two chicks currently with issues. A two week old is currently under a light and in a brooder with a Americana. I got both at the same time last week, they were at a chicken farm and both looked pretty rough. The Americana snapped back immediately and became a big puff ball. The Barred is still looking weak, listless, vent was dirty today. I cleaned her up, but she is still acting funny, while the other one is sitting sleeping, she is standing with wings hanging down. She doesn't look happy. She is on starter and is outside a little everyday.

Now my second issue is even more sketchy. We had a good health, happy flock, raised since babies, moved them outside to their coop and had a random bear attack, that left us with two survivors. One being "Itsy Bitsy", she was another farm rough one that my four year old loved and the farm gave to us for no charge. She never looked right, but I was hoping she would plump up and feather out. Now she is chirping all the time, I think she is traumatized from the bear attack. Still looks rough, missing feathers on wing and neck area, could be new feathers still in cuticle, but sketchy, and her crop never fills up like the others. I have been trying to feed her some scrambled egg to get some weight on her, but she only she interested in what the other survivor is doing or eating. She eating starter still and free ranged all day. I have been trying to feed her extra, but results not impressive. Anyway this is a good site and I have already found some good information, thanks.

 

[BLT1]

Just checked on barred 2wk old, it was standing up with it's head hanging down, it finally laid down. Cleaned water add some drops of apple cider vinegar, added more starter food. It pooped, I dipped it's beak into the water, it drank a little, was interested in the food. Took out the other chick because it is three times the size of the barred now. Barred ate, then started chirping for it's friend. Good night to all and good luck-

 

[Chambertin]

Sick chicks chirp alot when left alone. Makes me sad, but they need to be separated for their and everyone good.
Sure sounds like an internal problem, real sickness, but I dont know which one.

How's the poop, eyes, etc.?
I'm guessing you ruled out the obvious external parasites.
Some little ones bounce back in an instant, others take a little while, and still others gave up long ago but can hang on a while if you force them. Its sad, but I think some chicks just werent cut out for chicken life.
Do what you can, but dont feel bad if they pass on.

The older one is defiantly in shock.
I've heard that putting traumatized birds with chicks can help. Just watch them for the first while and make sure the big one doesnt peck the new girl. Kind of like finding an old veteran mentoring a young kid, helps them both and makes for a great movie.

Still, I havent had to do deal with a hen that stressed. Our hen cheered up a bunch when she saw the babies arrive home. Before that she had become depressed and didnt eat much because the rooster was a little over-testosteroned.
I think he'd mate a mop if you put a feather on it.
After she saw the pullets she started eating like a horse and almost outweighs the rooster now, still she has her mean days and we have to keep an eye out after she's mated for her pecking the little ones.