One chick won't stop crying

[WhitneyShaffley]

We have 5 chicks, 3 are 2 weeks old, 2 are 1 week. One of our week old chicks wont stop chirping unless she is held. The other 4 are fine and happy with the brood temp, I am using a heating pad and they all lay on it or in the cave under it, but she seems to lack the instinct to get under it or lay flat on top to warm up. She chirps loudly non stop, and doesn't seem to be growing like the other week old chick. We have them all on corid because we saw several diarrhea/mucus poops and blood in a poop, and she seemed lethargic.

I guess what I need help with is knowing how to care for her, since the others are content. At what point is it clear a chick isn't going to make it? Please help, I am very stressed and concerned for her.

 

[Cellomama2]

Just found this in another post a few minutes ago. https://www.backyardchickens.com/threads/baby-chick-isn’t-growing.1364721/