I recently hatched out a dozen chicks from my friends eggs and she is going camping so I had to babysit so I put them in my brooder and I bought a couple chicks from a lady down the road and ever since I mixed the chicks some have become lethargic and died. Only 2 of the chicks I bought are still alive and about 5 of the dozen are alive. What should I do? I haven't noticed any coughing or sneezing or anything other than they are just acting lazy and dying. I know my brooder is warm enough but this is stumping me.please help!