After poults are successfully introduced to food and water, and all other environmental needs are met, they are some pretty tough and lively customers. You might consider performing a gross necroscopy on one of those that dies and examine the trachea (a little young for heavy infestation but...
What variety of poults were these? Do you have more and, if so, are they behaving the same way? Temp./bedding type/kind of feed?
I'd get a hold of the hatchery you ordered them from. I could understand their arriving dead, or stressed and puny but, assuming you are up to speed on brooding...