Ah, I see. I've been tinkering around with it for a bit and I'm coming up with the same problem you're having. All of my homing bullets follow the first helicopter.
Maybe a new feature request for the Turret behavior? Like "Get Target UID?" Then you could do something like this, maybe:
+ Turret has target
- Turret: Spawn object Bullet
- Bullet: Set value('myTarget') to turret.TargetUID
+ Bullet: Value 'myTarget' Greater than 0
+ Group: Enemy Unique ID is bullet.Value('myTarget')
- Rotate 5 degrees toward Group: Enemy
Edit: Sweet Jesus, was I ever beaten. I've got to learn to check the thread again before hitting "submit."