Physics2D.IgnoreCollision not working!

In this project I want each enemy prefab to ignore each other's collision boxes (2D) but only the first to spawn ignores everyone else's collider. Please help. Attached is my enemy code and a video demonstration of the bug: https://youtu.be/XOAm6KTvtXY The code to note is line 22-24.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Depression : MonoBehaviour {
 
     private int speed = 5; //Speed of enemy
     private Rigidbody2D rb; //Enemies rigidbody
     private SpriteRenderer lookingRight; //Is the enemy facing right?
     private bool movingRight = true; //Is the enemy moving right?
     private GameObject clones; //Other cloned of the same enemy
 
     public static float health = 40f; //Enemies helath
     public TextMesh healthText; //Enemies health text display
 
     void Start(){
         rb = GetComponent<Rigidbody2D> (); //Get the rigidbody of the enemy
         lookingRight = GetComponent<SpriteRenderer> (); //Get the sprite renderer of the enemy
     }
 
     void Update(){
         clones = GameObject.FindGameObjectWithTag ("Depression"); //Finding other clones in game
 
         Physics2D.IgnoreCollision (GetComponent<Collider2D> (), clones.GetComponent<Collider2D> ()); //This allows the enemy type to pass through each other's colliders
 
         healthText.text = health.ToString(); //Set the health text to the current health of the enemy
 
         //Enemy movement
         if (movingRight) {
             rb.AddForce (transform.right * speed); //Moving right
         } else if (!movingRight) {
             rb.AddForce (-transform.right * speed); //Moving left
         }
 
         if (health <= 0f) { //If the enemy is at or below 0 health, destroy the enemy.
             Destroy (this.gameObject);
             Game_Manager.focus += 0.05f;
             //TODO: Make focus increment (per kill) relative to player's accuracy.
         }
     }
 
     void OnTriggerEnter2D(Collider2D other){ //Changing the direction of the enemy
         if (other.gameObject.tag == "Turn" && movingRight == true) { //If the enemy hits a trigger called "Turn", the enemy flips it's sprite on the x-axis and starts to move left
             movingRight = false;
             lookingRight.flipX = true;
         } else if (other.gameObject.tag == "Turn" && movingRight == false) { //If the enemy hits a trigger called "Turn", the enemy flips it's sprite on the x-axis and starts to move right
             movingRight = true;
             lookingRight.flipX = false;
         }
     }
 }

Thank you, Mika Joel.