i would call the hatchery, and ask them,, see what their response is,, because from my untrained eyes,, your doing everything right,, so dont blame yourself,,its got to be something WAY deeper then your care,,,tomorrow ill ask a few people to look at this thread and see what their thoughts...
are they piling up on each other?,, if you go near the brooder do they run into a corner fast and trample each other?
sorry for all the ?'s ,, but this seems weird,, something NOT right,, and it doesnt sound like anything your doing to them.