object pooler with delayed object pools

so i have made my generic object pooler script after following various guides and tips.

this is the script:

 using UnityEngine;
 using System.Collections;
 
 public class ObjectGenerator : MonoBehaviour {
 
     public Transform generationPoint, maxWidthPoint, minWidthPoint, player;
     public float distBetweenMin, distBetweenMax, playeroffsetX, maxWidthChange;
     public ObjectPooler[] theObjectPools;
     public bool chainSpawn = false;
     
     private float distBetween, minWidth, maxWidth, widthChange;
     private int objectSelector;
     private float[] objectHeights;
     
     void Start()
     {
         objectHeights = new float[theObjectPools.Length];
         
         for (int i = 0; i < theObjectPools.Length; i++)
         {
             objectHeights [i] = theObjectPools [i].pooledObject.GetComponent<BoxCollider2D> ().size.y;
         }
         
         maxWidth = maxWidthPoint.position.x;
         minWidth = minWidthPoint.position.x;
     }
     
     void Update()
     {
             SpawnObject();
     }
     
     void SpawnObject()
     {
         if(transform.position.y > generationPoint.position.y)
         {
             distBetween = Random.Range (distBetweenMin, distBetweenMax);
             objectSelector = Random.Range (0, theObjectPools.Length);
 
             if (!chainSpawn) 
             {
                 widthChange = player.transform.position.x + Random.Range (minWidth, maxWidth);
             } 
             else 
             {
                 widthChange = player.transform.position.x + Random.Range (maxWidthChange, -maxWidthChange);
 
                 if (widthChange > maxWidth) 
                 {
                     widthChange = maxWidth;
                 } 
                 else if (widthChange < minWidth) 
                 {
                     widthChange = minWidth;
                 }
             }
                 
             float z = transform.position.z;
             
             transform.position = new Vector3 (widthChange + playeroffsetX, transform.position.y - (objectHeights[objectSelector] / 2) - distBetween, z);
             
             GameObject newObject = theObjectPools[objectSelector].GetPooledObject();
             newObject.transform.position = transform.position;
             newObject.transform.rotation = transform.rotation;
             newObject.SetActive (true);
 
             transform.position = new Vector3 (player.transform.position.x, transform.position.y - (objectHeights[objectSelector] / 2), z);
         }
     }
 }
 

this script actually seems to work really well but as my game dev have gone further i have realised that it required another feature which is where i get stuck.

so what i need is to be able to have multiple pools of various objects (which i have), these object pools currently are all being accessed randomly using this part of the script

 objectSelector = Random.Range (0, theObjectPools.Length);

what i would like is to have the option to as time in the game goes by the various pools get activated, for example first i would like to spawn obj1 then say after a minute add obj2 pool (can now spawn randomly obj1 or obj2).

has anyone got any ideas?