Were the ones that died eating? Did they have full crops? I'm assuming they were incubator hatched, not hatched with a broody hen? How long were they in transit to you? Any chance they could have been chilled then?
This is very mysterious.
I saw the first one who died eat and drink just about one hour before she died. I don't know if she had a full crop or not as I don't know what that is. However she wasn't very interested in eating or drinking. She preferred to spend her time under the ecoglow sort of dozing towards the end.
I saw all of those who died being perfectly active, eating and drinking and running around. I witnessed them being 'normal' before I went to bed, and then in the morning about 9 hours later, I found them dead. All except for the first one who died at 3.30pm who I was with approx 45 mins before she died.
Yes, they were incubator hatched. We picked them up from the supplier and brought them home in a box. They were in the box for around 1 hour and 45 minutes. When I got them home I made sure they all got a drink of water and placed them in the brooder near the ecoglow, which they found pretty quickly. The temperature that day was around 21ºC ( 70ºF)
When the first one died I also thought maybe she had got chilled or stressed during the journey.
After aart mentioned coccidiosis I did some research here and on other sites. Maybe they had that - picked it up at the supplier. The research I did states that the death rate is highest around 4 days after initial contact with the protozoa through infected droppings or just through having it carried in on shoes, hands, etc. The research also says that if the chicken gets through day 6 after initial contact she will have built up an immunity to it. This ties in with how long the chicks were here before they started dying.
So now I'm hoping that my last remaining survivor has built this immunity and that she doesn't die tonight, if it truly IS cocci.
These are the first chickens I have ever had. The brooder that I have for the chicks is made from a dog crate with hardware cloth around it. After one died I put a plastic tote box (new and never before used) in the dog crate in case there was a draft. There was fresh wood shavings on the floor, and then after the 2nd one died I put fresh paper towels on top of the shavings, in case they had been eating the shavings and that was hurting them in some way.
Today the remaining chick was cheeping loudly while under the ecoglow a few times, so I made a sort of hill with the shavings and the paper towels under the middle of the heat plate so she could choose to lie closer to the plate or further away. Last time I checked on her (about an hour ago) she was lying on the top of the 'hill' with her back just touching the heat plate.
Even with the heat plate in the lowest position the chicks only actually touched it when standing up. The moment they squatted down they were no longer in contact with it. They used to sleep all together, side by side, under it. I don't know if this means they weren't warm enough or not. They didn't make any loud cheeping when under there. Only today when the last one was there on her own did she cheep loudly while under the ecoglow.
Thank you so much for your help and suggestions with all this...