The only thing I can think of is stress, especially if they were just shipped. Lots of people talk about bps going off feed for a while, but it has yet to happen to me, knock on wood. What are you keeping them in? do you have hides? and correct temps and everything. As long as your husbandry is good then I dont know what else there is to do besides wait...I know thats easier to say than do. Hopefully a member who has a little more experience than me will chime in too.
hope this helps