Maybe it's a good thing - they won't run up to strangers and get stolen. My niece's dog is very sociable and the kids in the neighbor all want to walk him and play with him. He would go off with complete strangers. If they don't "get over it" on their own, I would make a point of having welcome visitors offer then the same treats you d I know chickens don't use their brain much but maybe that would help them decide who is okay and who isn't.