They were in separate inclosures when I went to get them. The guy told me they were all 14 weeks but the Orpington seems a bit smaller.
Ahh, there's the clincher...so you are doing a bit of a 'single bird' integration here.
Often if all are put into a new place it removes the territoriality aspect,
but could be the maturity aspect is trumping that.
Might be good to have a separate enclosure so you can do some 'chicken juggling',
put the 'bully' birds in there and let the 'bullied' have free reign of the main coop and run for a few hours, then add one of the other birds to the main area and see what happens.
Mix and match between the two areas to throw the pecking order thing off a bit.
Pic of all of them together might tell the tale on age difference.
Here's some tips on integration that might help your situation.
Integration Basics:
It's all about territory and resources(space/food/water).
Existing birds will almost always attack new ones to defend their resources.
Understanding chicken behaviors is essential to integrating new birds into your flock.
Confine new birds within sight but physically segregated from older/existing birds for several weeks, so they can see and get used to each other but not physically interact.
In adjacent runs, spread scratch grains along the dividing mesh, best if mesh is just big enough for birds to stick their head thru, so they get used to eating together.
The more space, the better. Birds will peck to establish dominance, the pecked bird needs space to get away. As long as there's no copious blood drawn and/or new bird is not trapped/pinned down and beaten unmercilessly, let them work it out. Every time you interfere or remove new birds, they'll have to start the pecking order thing all over again.
Multiple feed/water stations. Dominance issues are most often carried out over sustenance, more stations lessens the frequency of that issue.
Places for the new birds to hide 'out of line of sight'(but not a dead end trap) and/or up and away from any bully birds. Roosts, pallets or boards leaned up against walls or up on concrete blocks, old chairs tables, branches, logs, stumps out in the run can
really help. Lots of diversion and places to 'hide' instead of bare wide open run.