Puffers can be really territorial, especially with each other. I had gotten one once and had to put it all by it's self. He was really happy ina 10 gallon all his own...that tiny silly little interesting creature ate nothing but snails...but since I had two large planted tanks there was never a shortage of food for him.
See if you can read up on them. I am not an expert on them but you might want to think about separating them or returning some if you can. Otherwise try arranging areas that give them the illusion of territory like tall plants and decor that break up their line of sight of one another and give the little ones a place to hide.