Were the 'new' chicks in this same coop and run before they went on their 'vacation'?
Are there any other birds involved?
Not sure they'll remember each other and have a 'happy reunion'.
11 days might not be
too long, and chickens do supposedly have a remarkable memory for faces, but they can also be rather(viciously) protective of their territory and resources.
I'd be ready to have a separate 'see no touch' area if needed...
wire crates can be very handy for this type of thing.
The 'basics' of lots of space, multiple water/feed stations, and places to 'hide' may be well employed here.
Best of cLuck!
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.