bullets kill all enemies, not just the ones hit.

Hi all, I have several enemies walking around my level chasing the player but when I shoot one, all of them take damage.

Here is my code attached to my bullet prefab

 public class Bullet : MonoBehaviour {
 
     public float lifeSpan = 3;
     static private Enemy myEnemy;
 
 
     // Use this for initialization
     void Start () {
 
         gameObject.GetComponent<CapsuleCollider>().isTrigger = true;
         StartCoroutine(kill());
 
         if ((myEnemy = GameObject.FindObjectOfType(typeof(Enemy)) as Enemy) ==null)
 
         {
             Debug.Log("No Enemies to Shoot!!");
         }
     
     }
 
     void OnTriggerEnter(Collider other)
 
     {
         if(myEnemy !=null)
 
         {
 
         if    (other.gameObject.tag == "Enemy")
 
             {
                 Debug.Log("Hit! " + other.name);
                 myEnemy.takeDamage(10);
                 Die();
             }
 
             else
 
             {
                 Debug.Log ("Hit! " + other.name);
                 Die();
             }
         }
 
     }
     // Update is called once per frame
     void Update () {
     
     }
 
     void Die()
 
     {
 
         Destroy(this.gameObject);
     }
 
     protected IEnumerator kill()
     {
         yield return new WaitForSeconds(lifeSpan);
         Destroy(gameObject);
     }
 }

and here is my code attacked to my enemy..

public class Enemy : MonoBehaviour {

 static private Player mainPlayer;
 public enum EnemyType{Green, Purple, Red};
 public float mHealth = 20.0f;
 private float mMaxHealth = 20.0f;
 [SerializeField]
 private EnemyType enemyType = EnemyType.Purple;


 void Awake()
     
 {
     if(mainPlayer == null)
     {
         
         if((mainPlayer = GameObject.FindGameObjectWithTag("Player").GetComponent<Player>()) == null)
         {
             if((mainPlayer = GameObject.FindObjectOfType(typeof(Player)) as Player) == null)
             {
                 Debug.LogError("Cannot locate main player");
             }
         }
     }
 }

 public void takeDamage(float amount)
     
 {
     mHealth -= amount;
     
     if(mHealth <=0)
         
     {
         dieEnemy();
     }
     
     
 }

 // Use this for initialization
 void Start () {
     initEnemy(enemyType);
 }
 
 // Update is called once per frame
 void Update () {
 

 
 
 }


 public void dieEnemy ()
 {
     Destroy (gameObject);
 }


 public void initEnemy(EnemyType newEnemyType)
 {
     switch(newEnemyType)
     {
     case EnemyType.Purple:
         mHealth = 20.0f;
         mMaxHealth = 15.0f;
         break;
     case EnemyType.Green:
         
         mHealth = 20.0f;
         mMaxHealth = 20.0f;
         break;
         
     case EnemyType.Red:
         
         mHealth = 20.0f;
         mMaxHealth = 10.0f;
         break;
         
     }
     
 }

}

Can anyone tell me why this is happening?

TIA.