How often is it sneezing and are all of them sneezing? Lose the bedding they came with, you'd do better with paper towels until you can get a block of shavings. You do not know who has touched it, what's in it, etc.. It should be clean but I've seen some funny stuff at TS. You need to make sure it's not an environmental issue first, then how often they are sneezing and how many of them are sneezing. An antibiotic at this age can be done if it is necessary, but it's much better to rule out all of the possibilities first, quickly, so that if it is something starting up you can hit it early.
You haven't said if you are doing medicated feed or not, if you are you don't want to give them the vitamins for more than a day at most. It messes up the ability of the amprolium to do it's job and keep the coccidia numbers down.
