Unity3d 4.6 javascript prefab with script

Hi I created a prefab named block1 and added a script on them named sheepController which does following:

 var startingHealth:int = 2;
 var currentHealth:int;
 
 var isDead:boolean;
 
 function Awake () {
     currentHealth = startingHealth;
 }
 
 public function HitSheep (sheep:GameObject) {
     
     Debug.Log("Hit Sheep startet");
     Debug.Log("Current Health: " + currentHealth);
     
     if (isDead)
     {
         Debug.Log("Sheep is dead");
         return;
     }
     
     //currentHealth = currentHealth - 1;
     currentHealth -= 1;
     Debug.Log("Current Health: " + currentHealth);
     
     if (currentHealth <= 0)
     {
         Debug.Log("Current Health <= 0");
         Destroy(sheep);
         Debug.Log("Destroy Sheep");
         isDead = true;
     }
 }

After that I instantiate the prefab (block1) in another script:

 function createBlocks()
 {       
         for(var j:int = -5; j<6; j++)
         {
             Instantiate(block1, Vector3(j*21, 20, 0), Quaternion.identity);
         }
 }

On Collision I like to subtract health of block1 by 1 each hit until it reached <= 0 .Then the block should be destroyed.

 function OnCollisionEnter(col:Collision)
 {    
     if (col.gameObject.tag == "block1")
     {
         Debug.Log("Hit Block1");
         audio.PlayOneShot(bricksound,0.2);
         
         var scontroller:sheepController;
         scontroller = GameObject.FindGameObjectWithTag("block1").GetComponent(sheepController);
         if (col.gameObject != null)
         {
             scontroller.HitSheep(col.gameObject);
 
         } else {
             Debug.Log("col.gameObject is null!");
         }
         
         if (gameController.score >= 0)
         {
             gameController.score = gameController.score + 10;
         }
     }
 }

The problem now the prefab count is not set for each prefab. It means if count is less then 0 on prefab hit it will be destroyed. I like to have each prefab has a start by 2 and subtracting by 1. Means two hits until destroy.

What I'm doing wrong? Thanks for help...