I bought 3 baby chucks about 2 weeks ago. 2 were 1 wk & the other was 2Weeks old. One developed pasty butt, I carefully cleaned her daily and more when needed. She started getting lethargic and eventually passed 2 days ago(this one also failed to thrive) Then I had another one that from one day to the next died (just got lethargic, couldn't stand and passed today) I contacted the place I bought the chicks from to ask advice..She said they may have caught a cold (our weather has been 80° one day.and then 40° the next) I had them in a pen in the garage under a lamp and when it was very cold I put a small heater. The cage is big enough for then to go.in & out of heat. So now I have I little chick left (she is about 5 wks) She is chirping and searching frantically for her "friends" just wondering if I should try to get a couple more chicks about her age, or raise her alone until I can get her.into a coop & then add more? This is my first time with chickens, just don't know what to do.