adopted a flock from shelter. some have leg mites but looks like some don't. Is that possible? Do I treat them all anyway? They have been together for at least two months- probably a lot longer than that. Also- my current crowd free ranges most of the day but mostly on a different part of my property. However, I did happen to catch a leghorn visiting the newbies in the barn stall. Since they don't even seem to be sharing with each other- are my guys ok if they are just looking form outside in?