I had a fox attack in the winter and so replenished my stocks, there was not too much falling out, but the three new ones never seemed to run with the group, they were always at the other end of the half acre field. So much so that the fox saw the opportunity of a lone hen and took one of them. I have had a new fence since then and no more foxes (touch wood), but I have always wondered why they don't stick together - they roost together fairly happily. Chicken personalities I guess, perhaps your group are a bit fussier than most, but I am sure they will settle soon - they are not as daft as people seem to think, are they!