Help please mysterious symptoms

I have a 3 week old bantam, I think it is a game bird variate. I purchased her from a feed store at a day old. She has grown fine and had no other issues until yesterday. I went gather up the chicks for their daily exercise time in the yard and she was very lethargic. This chick always runs and flaps and protest loudly when you go to pick her up. However, not yesterday, she just sat there not moving. I gathered her up wrapped her in a towel and looked her over no physical signs I can see. No fowl breath, no wheezing or sneezing. I fed her sugar water with an electro light booster. She would take a drink then close her eyes like it took all her energy. I have emptied her craw fed a small amount acv and given her a vitamin booster. I also noticed her feet are curled like a claw and won't stay out stretched. She was doing a gap mouth thing yesterday so I thought it might be gape worm. I administered 2 drops ivermectin to the back of the neck.I found her stool was black tarry and runny. Question what could this be? I have looked over symptoms and can't pin point the cause, she does seem some better today but still very lethargic and still curled up toes. (Side note I just got done with a 5 day treatment for cocci using corridor) This does not seem to be cocci based off what I have read. Any help I appreciate.

Could be a vitamin deficiency.
Separate her out and give her some B vitamins in her water, especially in Riboflavin(B2) you can find poultry vitamins at the feed store or give a Bcomplex vitamin in a pinch, just make sure it has no iron. Make sure she drinks well, you can add the vitamin water to some of her chick feed to make a wet mash to encourage her to eat.

https://www.backyardchickens.com/a/leg-foot-and-toe-issues-in-poultry-of-all-ages

http://www.thepoultrysite.com/publications/6/diseases-of-poultry/217/vitamin-b2-deficiency/
http://www.tillysnest.com/2014/03/vitamin-deficiencies-in-backyard-chicks-html/
http://www.thepoultrysite.com/articles/3508/importance-of-vitamins-in-poultry-production/

Wyorp Rock,
Sorry about that double post. Thanks I'll pick up some b specific vitamins and try that.

No problem
Sometimes if there is more than one thread started, it can be confusing for others (and you) when you get numerous answers.

How is she doing?

The chick is still hanging on improvement seems slow but her feet are no incurred and she is eating and drinking. She is still weak and sleeps more than her counterparts. I think she is getting spoiled lol she is in her own small brooder with a very young baby ameracauna chick. She cries loudly when I put her in with the other chicks but settles when held or placed in her own brooder. I have been calling her princess screech. I believe it is a vitamin deficiency she doesn't appear sick in any way just tired.

Sometimes it can be a slow process.
I'm glad to hear some improvement. Eating and drinking is good.
She probably does enjoy the extra TLC, they learn quickly how to manipulate their humans It's nice that she has a buddy to cuddle with.
Wishing you well and hoping she continue to improve.

Glad to report screech is well and back with her friends though she is a bit friendlier now.

Thank you for the update!
Glad to hear she is back with the others and doing well