Collision killing all enemies not the one the player collides with

As title says killing all enemies with tag enemy , all in Java

Fly (enemy) Collision Code:

 #pragma strict
 
 function OnCollisionEnter2D(collision2D: Collision2D ){
     var gameManager = GameObject.FindGameObjectWithTag("GameController");
     //var player = GameObject.FindGameObjectWithTag("Player");
     //var fly = GameObject.FindGameObjectWithTag("Fly");
     if (collision2D.gameObject.tag == "Player"){
         gameManager.SendMessage ("DeathFly");
     }
 }

GameManager code : (only the parts for the enemies as its a long script)

 #pragma strict
 
 var fly : GameObject;
 
 function DeathFly(){
     fly = GameObject.FindGameObjectWithTag("Enemy");
     fly.SendMessage("Kill");
 }
 
 

Fly (enemy) Code :

 #pragma strict
 
 var damage : int = 10;
 var health : int = 10;
 var hitSound : AudioClip;
 var flySound : AudioClip;
 var deathSound : AudioClip;
 var Boost : GameObject;
 
 var healthBar : UI.Slider;
 
 function Update(){
     var audio : AudioSource = GetComponent.<AudioSource>();
     if(health == 0){
         AudioSource.PlayClipAtPoint(deathSound, Camera.main.transform.position);
         Kill();
     }
 
     healthBar.value = health;
 }
 
 function Kill(){
     Boost = Instantiate(Resources.Load("Prefabs/Cloud"), transform.position, transform.rotation) as GameObject;
     Destroy(this.gameObject);
 }
 
 function ApplyDamage(){
     health = health -= damage;
 }

if anyone could help with killing when landing on the head i would be very great full.