You would make a new object and name the type “Bullet Parent”.
Don’t add this object to the game.
Then in the knife object, go to parent and set Bullet Parent as the Parent.
Use a collision in the Enemy objects and set the collision to Bullet Parent.
So whenever you make a new bullet type for different towers, you just set the parent to Bullet Parent. The enemy will recognize the collision between the different bullet types.
Got to looking around why the value would be stacking like that.
All 5 bundles in your Spawn Operator is outputting spawn. Each bundle uses the same mailboxes and messages that get sent at the same time.