4 weeks is a good period of see but don't touch, so that should've helped them acclimate...
Any photos of your set up? Both coop and run and how the younger birds are situated next to adults?
Agreed, this would be the first step. Once the adult birds are no longer as interested in the younger birds, you can try taking the fence down and supervising to see how well they get along.
At that point in time it's very helpful to have a lot of clutter around to provide hiding spots for...