Finding the closest player and making an action happend when player is in range

Hi!

I'm trying to create a maze with walls appearing when you are within a range of them. It works perfectly with one person but I'm creating a multiplayer game. It appears that only some walls works with this when there is more than one player.

Here is my code if you wanna have a look at it. It will probably explain more then I can do:

 using UnityEngine;
 using System.Collections;
 
 public class AppearWhenNear : MonoBehaviour {
 
     public GameObject[] players;
     public float distance = 5.0f;
     public float speed = 1.0f;
     public Vector3 targetPos;
     Vector3 startPos;
 
     float nearestDistanceSqr = Mathf.Infinity;
     GameObject closestGO;
 
     void Start () {
         targetPos = new Vector3(transform.position.x, 2.5f, transform.position.z);
         startPos = transform.position;
     }
 
     void Update () {
         players = GameObject.FindGameObjectsWithTag ("Player");
 
         if(closestGO != null) {
             if(Vector3.Distance(transform.position, closestGO.transform.position) < distance) {
                 Vector3 pos = Vector3.Lerp(transform.position, targetPos, speed * Time.deltaTime);
                 transform.position = pos;
             }
             else {
                 Vector3 pos = Vector3.Lerp(transform.position, startPos, speed * Time.deltaTime);
                 transform.position = pos;
             }
         }
 
         foreach(GameObject player in players) {
             float dist = (player.transform.position - transform.position).sqrMagnitude;
             if(dist < nearestDistanceSqr) {
                 closestGO = player;
                 Debug.Log(closestGO.name);
                 nearestDistanceSqr = dist;
             }
         }
     }
 }
 

Thank you //Proximal Pyro