Only one of all my Enemies shoots, Help please.

I am working in a top down view 2D shooter, I am mixing some 3D models and 2D sprites. I managed to get collision from lasers to the enemies no problem, the part I am stuck at is that I want my enemies to shoot at me. I have a script which is working properly, tank turrets that rotate towards the player and supposedly shoot.

My problem is that when I have 2 or more tanks, only one of the tanks will shoot. I mean, all the tanks aim at the player, but only will shoot. I did notice something, though, every time a new tank is added to the scene, the only tank that shoots seems to do it faster. I think it is shooting according to the number of tanks in the scene and what I want is every thank to shoot on its own.

I will post the code that I have for the what I need.

Any help will be greatly appreciated.

 using UnityEngine;
 using System.Collections;
 
 public class tankShoots : MonoBehaviour 
 {
     private float baseTime = 30.0f;
     private float coolDown = 1.0f;
     private float timeReset = 30.0f;
     private float zeroTime = 0.0f;
     private GameObject tankGun;
 
     public GameObject tankProjectile;
     // Use this for initialization
     void Start () 
     {
         tankGun = GameObject.FindGameObjectWithTag("tankGun");
     }
     
     // Update is called once per frame
     void Update () 
     {
         tankShooting();
     }
 
     void tankShooting()
     {
         baseTime -= coolDown;
         if(baseTime <= zeroTime)
         {
             Instantiate(tankProjectile, tankGun.transform.position, tankGun.transform.rotation);//tankGun.transform.rotation);
             baseTime = timeReset;
         }
     }
 }