Hiding a GUI Texture upon death.

Hello everyone. I am working on a very basic game as I am very new to Unity and also C# scripting. I have a GUI texture duplicated 3 times to display 3 heart icons. I want to remove one heart icon every time an enemy touches the player. Here is what I have so far :

 using UnityEngine;
 using System.Collections;
 
 public class PlayerDeath : MonoBehaviour {
 
 
     Vector3 spawnPoint;
     public int life = 0;
     public Transform respawnPosition;
     public int lives = 0;
     public GUITexture life1;
     public GUITexture life2;
     public GUITexture life3;
     void Start()
     {
         GameObject spawnObject = GameObject.FindWithTag("Player");
         spawnPoint = spawnObject.transform.position;
         }
 
     public IEnumerator OnCollisionEnter(Collision boom) 
     {
 
         //If the object that triggered this collision is tagged "bullet"
         if(boom.gameObject.tag == "Enemy")
         {
             life = 50;
             if(life == 50){
 
                 renderer.enabled = false;
             yield return new WaitForSeconds(5);
             renderer.enabled = true;
             transform.position = spawnPoint;
                 lives ++;
             }
 
             if (lives == 1){
                 life1.gameObject.SetActive = false;
             }
 
             if (lives == 2){
                 life2.gameObject.SetActive = false;
             }
 
             if (lives == 3){
                 life3.gameObject.SetActive = false;
             }
 
         }
     }
 
 
 }

When the player dies nothing happens, any ideas or advice? Thanks in advance :D