Can anyone give me a little advice, I have some chicks I am trying to get out of the house, two 7 1/2 week olds, three almost 5 week olds, and 5 three week olds. I figured now was the time so they can acclimatize, I put the older two groups out but kept the three week olds in. It got down to about 56 degrees last night, which I wouldn't think would be too cold. This morning one of the 5 week olds was very lethargic looking, so I brought it in the house. It hasn't moved all day, eyes closed unless I pick it up and move it around. I forced some baby vitamins and a little water down it but I don't dare do much since I have no idea what is wrong, I have it next to the brooder so it gets some heat from the brooder lamp. Worried I am going to lose it- this is the only splash Isbar that hatched.

Anyway my question is, was it too cold last night for them? Should I bring the 5 week olds back in? In a couple of nights it is supposed to be down in the lower 40s. Is THAT too cold and should I bring them in then? I read a good rule of thumb was 4 week olds could take 40 degrees, but now I am seriously doubting that.
Anyone think this is hypothermia in the chick, and if so is there anything I can do besides wait?
Rinda