and Welcome To BYC! Sorry about the lost chick 
Good luck with the other chicks!
you might want to post in the Emergencies forum also https://www.backyardchickens.com/f/10/emergencies-diseases-injuries-and-cures Do you know how old the chicks are, what are you using for a heat source and are you using a thermometer to check the temperatures? ... and pictures of your brooder set up etc might help. Shipping stress is pretty common, it is not unusual for chicks to get chilled this time of year on the way to the store, and if the shipment is slow they can be underway for 2-3days. Be sure the other chicks are eating and drinking, you might still want to put Chick Saver or some sugar in their water (1tsp/quart) for a day or so. If they are babies they should be too young for Mareks (generally need to be at least 3-4 weeks old to show symptoms), nice article from the Learning Center on it https://www.backyardchickens.com/a/the-great-big-giant-mareks-disease-faq
