While you may indeed have just gotten very skittish EE's, from my experience adding any new bird to an existing flock will cause the new bird to act skittish as they become a target for the pecking order (that's very unsettling to any bird). Integrating several new birds together, whether they were raised together or not, will usually cause them to form a subgroup by themselves. (Safety in numbers as you "crash" the new neighborhood.)
It takes awhile for the new birds to settle into an existing flock; and the existing flock to accept them, and for the new pecking order to be figured out.
I have had several "sub-flocks" for several months until they all finally adjusted to the new pecking order and everyone integrated together.
It can be a tall order for the new birds to adjust to you and the new flock. It can help to segregate out the new birds for a bit while they become accustomed to you (giving them treats by hand), then slowly integrate them into the flock. Avoid giving treats to the new birds in front of the existing flock (if they are together in one run) as that will likely cause aggression from the existing birds towards your new EE's in competition of your treats.
Often letting them live in subdivided pens where they can see each other but not touch is a good way for them to get used to each other, and to you. You know when its time to integrate as your existing birds get comfortable with them on the other side of the fence. Then add the new birds at night onto the roosts (by your calmest birds) can help with the integration.
But it will still take awhile for new birds to fully integrate. The good news is that it sounds like your EE's are nervous but not being overly hazed (no bodily injuries). However do watch out as being chased all the time by birds of your existing flock can make for a very nervous bird..
Time, and enough food treats judiciously given, usually helps everyone warm up, and you will probably see much more relaxed EE's....unless their temperament is indeed just skittish.
Lady of McCamley