Question about AI in MMORPG

Hi guys! I'm currently making a Co-op Zombie Apocalypse Survival Game.

But there's on problem. The Zombie follow just the newest GameObject with "Player" Tag. not the old one :/ Is there any way to fix it?

Btw Here's the Script i tried:

 using UnityEngine;
 using System.Collections;
 
 public class EnemyAI : MonoBehaviour
 {
     public int minRange;
     public bool follow;
     public float moveSpeed;
     public float rotationSpeed;
     private Transform myTransform;
     public Transform player;
 
     void Start()
     {
         myTransform = transform;
         player = null;
     }
 
     void Update ()
     {
        if(Vector3.Distance(GameObject.FindWithTag("Player").transform.position, myTransform.position) < minRange)
         {
             player = GameObject.FindWithTag("Player").transform;
             follow=true;
         }else{
             follow=false;
         }
 
         if(follow && player != null)
         {
             myTransform.rotation = Quaternion.Slerp(myTransform.rotation, Quaternion.LookRotation(player.position - myTransform.position), rotationSpeed * Time.deltaTime);
             myTransform.position += myTransform.forward * moveSpeed * Time.deltaTime;
         }
     }
 }

Any Ideas :)?