two remaining chicks, Noel and Nina (brahma and cochin), are weak, unstable, and seem very "groggy". I brought them inside and cleaned the coop. Nina's condition has been deteriorating while Noel is recovering....It may be coccidiosis but there is no and there hasn't been any blood in their stools. It gets pretty chilly here at night so we still have their lamp set up.
How are your chicks doing @SilkiesInSuburb ?
I'm sorry to hear that you lost one. I agree that bringing them in to get them warm was a very good idea.
What type of food/treats do you feed?
It's possible they may have gotten too cold, but it's a good idea to consider Coccidiosis as @Sagenovese suggested. Do you have photos of their droppings? Coccidiosis does not always present with bloody stool - there are several strains of Coccidiosis in chickens and if I remember correctly only 1presents with blood. Symptoms include - lethargy, huddling/puffed up appearance, going off food/water, loss of balance and loose stools with mucous or blood. Corid is a coccidiostat that can be found at most feed stores like Tractor Supply, it's very mild and won't hurt them if you choose to treat.
If they have bounced back/improved with heat, getting hydrated and eating, then most likely they were chilled and dehydrated.
Let us know how they are.

