So they are about 4 weeks old now, right? Give them a solid 4 weeks enclosed 24/7 in coop. This is done so that they have a solid understanding that this is home. Then you let one out for the day. If he goes back in, the next day you let 2 out-etc.
Don't skip this or you'll have tree roosters...
I'd go a bit further than just inside, otherwise you may be chasing 3 more. You want to be not so close as to threaten them but close enough to shut that entry once they go in.
As long as the ones you caught are enclosed but visible, the escapees are going to stay close.if you have a fishing net handy, now's a good time to use it.
Barring that: I don't know how your set up is. If you can entice the ones inside to eat in view of the others and it is possible to then...