Enemy clones not destroying after a certain number of clones.

I am making a survival game. Everything is working fine. My enemy prefab is tagged as enemy. Every time enemy health goes to zero they get destroyed and disappear. But after a certain number of clones when their health goes to zero the stop moving but they don't disappear from the scene.

Here is my enemyHealth code :

 Animator anim;
 AudioSource enemyAudio;
 ParticleSystem hitParticles;
 CapsuleCollider capsuleCollider;
 bool isDead;
 bool isSinking;


 void Awake ()
 {
     anim = GetComponent <Animator> ();
     enemyAudio = GetComponent <AudioSource> ();
     hitParticles = GetComponentInChildren <ParticleSystem> ();
     capsuleCollider = GetComponent <CapsuleCollider> ();

     currentHealth = startingHealth;
 }


 void Update ()
 {
     //if(isSinking)
     //{
       //  transform.Translate (-Vector3.up * sinkSpeed * Time.deltaTime);
     //}
 }


 public void TakeDamage (int amount, Vector3 hitPoint)
 {
     if(isDead)
         return;

     enemyAudio.Play ();

     currentHealth -= amount;
         
     hitParticles.transform.position = hitPoint;
     hitParticles.Play();

     if(currentHealth <= 0)
     {
         //isDead = true;
         //Destroy (GameObject.FindGameObjectWithTag ("Enemy"));
         //enemyAudio.clip = deathClip;
         //enemyAudio.Play ();
         //ScoreManager.score += scoreValue;
         Death ();
     }
 }


 void Death ()
 {
     isDead = true;

     //capsuleCollider.isTrigger = true;

     //anim.SetTrigger ("Dead");

     Destroy (GameObject.FindGameObjectWithTag ("Enemy"));
     ScoreManager.score += scoreValue;
     enemyAudio.clip = deathClip;
     enemyAudio.Play ();
 }


 //public void StartSinking ()
 //{
   //  GetComponent <NavMeshAgent> ().enabled = false;
     //GetComponent <Rigidbody> ().isKinematic = true;
     //isSinking = true;
     
    // Destroy (gameObject, 2f);