How can I add parallax to background sprites which are being instantiated only in play mode.

I've looked for this everywhere but none suits to my situation here:

So my 2d endless game has 2 layers of mountains in the background which I want to add parallax on, the Near layer needs to be slower than actor/camera, & the Far to be slowest. The problem is, I can't directly add script of movement to them as they are instantiated in play mode of random color selection according to the random theme colors, so they are being created one after other from the script below, but I want to add a movement on them on x axis slower than camera speed, while also letting it recreate continuously at the end of last one.

Here's the script creating new mountains :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;

 public class PathManager : MonoBehaviour {

 public static PathManager Instance;
 public GameObject CoinFragments;
 public GameObject SlideArrow;

 public float parallaxSpeed = 5f; //

 private GameObject lastPathObject;
 private float PathXPosition;

 private GameObject lastMountainFar;
 private float MountainFarXPosition;
 private GameObject lastMountainNear;
 private float MountainNearXPosition;

 private float StarXPostion;

 private float lastCameraX;  //

 // Use this for initialization
 void Start () {
     Instance = this;
 }

 // Update is called once per frame
 void Update()
 {
                                         
 }


 private void LateUpdate()
 {
     // Check for new Near Mountain
     if (lastMountainNear != null && GamePlayCameraManager.Instance.MainCamera.transform.position.x > lastMountainNear.transform.position.x)
     {
         this.GenerateNearMountain();
     }

     // Check for new Far Mountain
     if (lastMountainFar != null && GamePlayCameraManager.Instance.MainCamera.transform.position.x > lastMountainFar.transform.position.x)
     {
         this.GenerateFarMountain();
     }
 }



 // Start Creating Mountains
 public void StartMountainCreation(){
     MountainNearXPosition = GamePlayCameraManager.Instance.MainCamera.transform.position.x;
     MountainFarXPosition = GamePlayCameraManager.Instance.MainCamera.transform.position.x;
     this.GenerateNearMountain();
     this.GenerateFarMountain();
 }

 private void GenerateNearMountain(){
     Vector3 MountainPosition = new Vector3(MountainNearXPosition - 4f, -3.6f, 10f);
     lastMountainNear = Instantiate(ThemeManager.Instance.SelectedMountainNear, MountainPosition, Quaternion.identity);
     MountainNearXPosition = MountainNearXPosition + lastMountainNear.GetComponent<Renderer>().bounds.size.x - 0.01f;
  
     //float deltaX = GamePlayCameraManager.Instance.MainCamera.transform.position.x - lastCameraX;
     //lastCameraX = GamePlayCameraManager.Instance.MainCamera.transform.position.x;
     //lastMountainNear.transform.position += Vector3.right * (deltaX * parallaxSpeed);
 }

 private void GenerateFarMountain(){
     Vector3 MountainPosition = new Vector3(MountainFarXPosition - 4f, -3.6f, 22f);
     lastMountainFar = Instantiate(ThemeManager.Instance.SelectedMountainFar, MountainPosition, Quaternion.identity);
     MountainFarXPosition = MountainFarXPosition + lastMountainFar.GetComponent<Renderer>().bounds.size.x - 0.01f;
 }
    

Here's my camera movement script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;

 public class GamePlayCameraManager : MonoBehaviour {

 public static GamePlayCameraManager Instance;   // Singleton Instance
 public Camera MainCamera;   // Main Camera

 private Vector3 offset;

 // Use this for initialization
 void Start () {
     Instance = this;
     MainCamera.transform.position = new Vector3(0, 0, -10);
 }
 
 // Update is called once per frame
 void Update () {
     
 }

 void LateUpdate()
 {
     if (GameStateManager.GameState == GameState.Set || GameStateManager.GameState == GameState.Playing)
         MainCamera.transform.position = new Vector3(this.offset.x + ActorManager.Instance.Actor.transform.position.x + 0.8f, 0, -10);
 }

 // Fixed Update Method
 void FixedUpdate(){

 }

 public void FindCameraOffset(){
     this.offset = ActorManager.Instance.Actor.transform.position - MainCamera.transform.position + new Vector3(1.5f, 0f, 0f);
 }
 }