OnCollisionExit dont working

I trying to make a Bubble Shooter game, my bubbles freezes all your transform position when collide with some tags, but i want this bubbles fall when nothing touching it, to stop my bubbles float in scenario and just make it fall to the ground. I use OnCollisionEnter to make it, and trying to use OnCollisionExit, but didnt work, any idea?

     private void OnCollisionEnter(Collision collision) {
         if(collision.gameObject.tag == "Blue" || collision.gameObject.tag == "Red" || collision.gameObject.tag == "Green" || collision.gameObject.tag == "Yellow" || collision.gameObject.tag == "Roof") {
             _rigidbody.constraints = RigidbodyConstraints.FreezeAll;
             _shootProjectile.GetComponent<ShootProjectile>().ShowNext();            
         }
         else if(collision.gameObject.tag == "Destroy") {
             StartCoroutine(DestroyOnGround());
         }
         else {
             _rigidbody.constraints = RigidbodyConstraints.None;
             _rigidbody.useGravity = true;
             
         }
 
     }
     private void OnCollisionExit(Collision collision) {
         _rigidbody.constraints = RigidbodyConstraints.None;
         _rigidbody.useGravity = true;
     }