Trouble with apply damage to enemy

I have a script attached to my projectile, and a script attached to all the enemies.

The script attached to my projectile, if the projectile hits a transform with a tag "Enemy", then apply damage by accessing the healthscript of the enemy. But lets say I have 4 of the prefab enemy in a line.. I shoot the first one repeatedly, (the 4th one dies, then the 3rd, then the 2nd, and finally the 1rst one dies) How do I get it to where each one has it's own health? Here is the two scripts I have so far.

 using UnityEngine;
 using System.Collections;
 
 /// <summary>
 /// 
 /// This is the 7.5mm bullet script.
 /// 
 /// This script is attached to the 7.5mmBullet.
 /// 
 /// </summary>
 
 public class RifleBullet : MonoBehaviour {
     
     //----------Variables Start-------------
     
     //A quick reference.
     private Transform myTransform;
     
     //The projectiles flight speed.
     private float projectileSpeed = 10;
     
     //Prevent the projectile from causing
     //further harm once it has hit something.
     private bool expended = false;
     
     //A ray projected in front of the projectile
     //to see if it will hit a recognisable collider.
     private RaycastHit hit;
     
     //The range of that ray.
     private float range = 1.5f;
     
     //The life span of the projectile.
     private float expireTime = 5;
     
     
     //--------------Variables End------------------
     
     
     // Use this for initialization
     void Start () 
     {
         myTransform = transform;
         
         //As soon as the projectile is created start a countdown
         //to destroy it.
         StartCoroutine(DestroyMyselfAfterSomeTime());
     }
     
     // Update is called once per frame
     void Update () 
     {
         //Translate the projectile in the up direction (the pointed
         //end of the projectile).
         myTransform.Translate(Vector3.up * projectileSpeed * Time.deltaTime);
         
         
         //If the ray hits something then execute this code.
         if(Physics.Raycast(myTransform.position,myTransform.up, out hit, range) &&
            expended == false)
         {
             //If the collider has the tag of Floor then..
             
             if(hit.transform.tag == "Enemy")
             {
                 //If hit and enemy, destroy self.
                 Destroy(myTransform.gameObject);
                 
                 //Access the AnimalHealhBar Script to apply damage.
                 GameObject zombie = GameObject.Find("Zombie");
                 AnimalHealthbar aHealthScript = zombie.GetComponent<AnimalHealthbar>();
                 aHealthScript.wasHitByRifle = true;
             }
         }
     }
     
     
     IEnumerator DestroyMyselfAfterSomeTime()
     {
         //Wait for the timer to count up to the expireTime
         //and then destroy the projectile.
         yield return new WaitForSeconds(expireTime);
         
         Destroy(myTransform.gameObject);
     }
 }

And this is the Enemy's health script.

 using UnityEngine;
 using System.Collections;
 
 public class AnimalHealthbar : MonoBehaviour {
     
     //-------------Variables Start---------------
     
     
     //The health bar texture is attached to this in the inspector.
     public         Texture     healthTex;
     
     //Quick references.
     private     Camera         myCamera;
     private     Transform     myTransform;
     private     Transform     triggerTransform;
         
     //These are used in determining whether the healthbar should be drawn
     //and where on the screen.
     private     Vector3     worldPosition            = new Vector3();
     private     Vector3     screenPosition          = new Vector3();
     private     Vector3     cameraRelativePosition     = new Vector3();
     
     private     float        minimumZ                 = 1.5f;
     
     
     //These variables are used in defining the health bar.
     public         int         labelTop                 = 18;
     public         int         labelWidth                 = 110;
     public         int         labelHeight             = 15;
     public         int         barTop                     = 1;
     public         int         healthBarHeight            = 5;
     public         int         healthBarLeft             = 110;
     public         float         healthBarLength;
     public         float         adjustment                 = 1;
     
     //Value of health and HealthBar
     public         float         myHealth;
     public         float         maxHealth                 = 100;
 
     public         bool         iWasHit                    = false;
     
     private     GUIStyle     myStyle                 = new GUIStyle();
     
     public         bool         wasHitByRifle             = false;
     public         bool         wasHitByAK                 = false;
     
     
     //------------------Variables End------------------
     
     void Start ()
     {
         myHealth = 100;
         
         //Reference to our transform.
         myTransform = transform;
         //Reference to Camera's transform.
         myCamera = Camera.main;
         
         //FontSize
         myStyle.fontSize = 12;
         //FontSyle set to Bold.
         myStyle.fontStyle = FontStyle.Bold;
         
         //Allow the text to extend beyond the width of the label.
         myStyle.clipping = TextClipping.Overflow;
     }
     
     
     // Update is called once per frame
     void Update () 
     {    
         //Figure out how long the health bar should be and to avoid a mathematical error set
         //the health bar length to 1 if the the player's health falls below 1.
         
 
         if(myHealth >= 1)
         {
             healthBarLength = (myHealth / maxHealth) * 100;    
         }
         
         
         if(myHealth <= 0)
         {
             Destroy(myTransform.gameObject);
         }
         
         
         if(wasHitByRifle == true)
         {
             //Create the function to take away 55-90 health.
             myHealth -= (Random.Range(55,100));
             wasHitByRifle = false;
         }
         
         if(wasHitByAK == true)
         {
             //Create the function to take away 55-90 health.
             myHealth -= (Random.Range(4,8));
             wasHitByAK = false;
         }
     }
     
     void OnGUI ()
     {
         //Only display the player's name if they are in front of the camera and also the 
         //player should be in front of the camera by at least minimumZ.
         
         if(cameraRelativePosition.z > minimumZ)
         {
             //Set the world position to be just a bit above the player.
             worldPosition = new Vector3(myTransform.position.x, myTransform.position.y + adjustment,
                                         myTransform.position.z);
             
             //Convert the world position to a point on the screen.
             screenPosition = myCamera.WorldToScreenPoint(worldPosition);
             
             
             //Draw the health bar and the grey bar behind it.
             GUI.Box(new Rect(screenPosition.x - healthBarLeft / 2, 
                              Screen.height - screenPosition.y - barTop,
                              100, healthBarHeight), "");
 
             GUI.DrawTexture(new Rect(screenPosition.x - healthBarLeft / 2,
                                      Screen.height - screenPosition.y - barTop,
                                      healthBarLength, healthBarHeight), healthTex);        
 
         }
     }
 }