Did you change the bedding? I wouldn't worry to much unless they have a colored discharge coming from the nasal area. I would just keep a eye on them for a few days and see if anything changes. Good Luck
Hard to day if they brought something with them or if they are reacting to dusty bedding, environmental irritants, etc. If they are having a snotty discharge, it most likely is something contagious. Were all those birds together when you got them or did they come from different places? I ask because one group may have given something to the other group.