could be an issue if there is not enough adequate hiding spots and if the newbies are not close to the same size. other than that, should be no problem, just a matter of time till they start shoaling together. That and hopefully you have a big enough tank.
My 5 inch reds got tail nipped for about a week when I tossed in my 8 inch yellow tern, but then they started to get along and he shows them the ropes, so to speak.