When we buy day old chicks from a feed store that had just come in the USPS that day or the day before, they are all suffering to a certain extent from shipping stress, including dehydration.
Then when you buy them and bring them home, that adds more stress on top of the first stress. I've gotten new chicks home, installed them in the brooder, and saw them collapse into prostrate and limp half alive pathetic things. I have no doubt at all, they would have died if I hadn't been prepared with my concoction of sugar water and Poultry Nutri-drench.
I pick up each chick and syringe the high glucose nutrition into each chick, repeating it each half hour until the chicks are racing around like normal chicks.
This time of year, most deaths of new chicks are from shipping stress that people don't recognize as the life threatening issue that it is until it's too late.