Spawning Bug.

Okay I have a game which involves spawning. My spawn points are both left and right. I have this wave that spawns once "delay" is completed. I am spawning moving object that does get destroyed. (which I am trying to do) At first it seems nice, no problems but after a few minutes (2 mins) it suddenly starts spawn 1000 upon 1000's of my moving objects. How would I stop this!!! I think it may be because I haven't got a destroy script, to destroy the moving objects, but I'm no genius! Please if anyone can help it would be much appreciated. Thank you!!! Here's my script:

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;

  [System.Serializable]
  public class WaveAction
  {
  public string name;
  public float delay;
  public Transform prefab;
  public int spawnCount;
  public string message;
    }

  [System.Serializable]
  public class Wave
  {
  public string name;
  public List<WaveAction> actions;
   }



  public class WaveGenerator : MonoBehaviour
  {
   public float difficultyFactor = 0.9f;
   public List<Wave> waves;
   private Wave m_CurrentWave;
   public Wave CurrentWave { get {return m_CurrentWave;} }
   private float m_DelayFactor = 1.0f;
   public GameObject ObjectToSpawn; 
 
   IEnumerator SpawnLoop()
   {
      m_DelayFactor = 1.0f;
      while(true)
      {
          foreach(Wave W in waves)
          {
             m_CurrentWave = W;
             foreach(WaveAction A in W.actions)
             {
                 if(A.delay > 0)
                     yield return new WaitForSeconds(A.delay * m_DelayFactor);
                 if (A.message != "")
                 {
                     // TODO: print ingame message
                 }
                 if (A.prefab != null && A.spawnCount > 0)
                 {
                     for(int i = 0; i < A.spawnCount; i++)
                     {
                         
                         // Random position within this transform
                         Vector3 rndPosWithin;
                         rndPosWithin = new Vector3(Random.Range(-1f, 1f), Random.Range(-1f, 1f), Random.Range(-1f, 1f));
                         rndPosWithin = transform.TransformPoint(rndPosWithin * .5f);
                         Instantiate(ObjectToSpawn, rndPosWithin, transform.rotation);  
                         
                     }
                 }
             }
             yield return null;  // prevents crash if all delays are 0
         }
         m_DelayFactor *= difficultyFactor;
         yield return null;  // prevents crash if all delays are 0
     }
 }
 void Start()
 {
     StartCoroutine(SpawnLoop());
 }
 

}