I have the quest in my topic title. I have raised SPECIAL stats of 16 dwellers and have since raised 6-8 more however the objective wont update for the last two needed.

Anyone know how to fix this? Its for a lunch box and it annoying the stuff out of me not being able to finish this.

Every time I've had that one it has had to be 18 different dwellers. Try rotating your dwellers and see if that does the trick.