Control when instantiated objects can move.

Hello. I am making a clone of the "Don't touch the white tile game" and it's all running smoothly, but I seem to be stuck on trying to limit which "black" tile moves them all down. I want it to be only when I touch the black block on the bottom that executes the command to move them all.

Currently when I touch any black block it'll move it down. I need some type of method to prevent anything higher than 0f cannot execute the "move" command. using UnityEngine; using System.Collections; using System.Collections.Generic;

 public class Movement : MonoBehaviour {
     public Instantiate bringInstantiate = new global::Instantiate ();
     private SoundFX importSound = new SoundFX ();
     private ScoreLog importScore = new ScoreLog();
     private string importScorelog = ScoreLog.currentScore.ToString();
     private int touchCounter;
     private GameObject[] grabBlackClonesArray;
     private Vector3[] vectors = new Vector3[4];
     private Vector3 selected;
     private int randomNumber;
     private bool correctTouch;
 
 
     public void Awake()
     {
                 //Create vector Positions
                 this.vectors [0] = new Vector3 (0f, 3.75f, -1.5f);
                 this.vectors [1] = new Vector3 (1.25f, 3.75f, -1.5f);
                 this.vectors [2] = new Vector3 (2.5f, 3.75f, -1.5f);
                 this.vectors [3] = new Vector3 (3.75f, 3.75f, -1.5f);
 
         }
 
     
     void Start()
     {
         //We set the array to have slots 0,1,2,3 (total of 4)
         grabBlackClonesArray = new GameObject[5];
 
         //We debug to see if the position 0 is not null
         Debug.Log (grabBlackClonesArray[0]);
 
 
 
     }
 
 
     
 
     
     
     
     void Update() {
 
         int randomNumber = Random.Range (0, 4);
         this.selected = this.vectors [randomNumber];
 
 
 
 
 
         importScorelog = ScoreLog.currentScore.ToString();
 
         //Vector3[] newlocation = 
 
         //We finally set grabBlackClonesArray and fill it up with all objects
         //with the tag "BlackTile"
 
         grabBlackClonesArray = GameObject.FindGameObjectsWithTag("BlackTile");
 
         //We check to see if it is true
 
         //To make sure that the movement is only done once we put it in a loop
         //remember we are in the Update method..it's called every frame
         if(grabBlackClonesArray[0].transform.position.y <= -1.25f) {
             Debug.Log ("clicked and ran <= 0.f");
             grabBlackClonesArray[0].transform.position = selected;
         }
         if(grabBlackClonesArray[1].transform.position.y <= -1.25f) {
             Debug.Log ("clicked and ran <= 0.f");
             grabBlackClonesArray[1].transform.position = selected;
         }
         if(grabBlackClonesArray[2].transform.position.y <= -1.25f) {
             Debug.Log ("clicked and ran <= 0.f");
             grabBlackClonesArray[2].transform.position = selected;
         }
         if(grabBlackClonesArray[3].transform.position.y <= -1.25f) {
             Debug.Log ("clicked and ran <= 0.f");
             grabBlackClonesArray[3].transform.position = selected;
         }
         //We need to grab the touch on Android Devices
         if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began || Input.GetKeyDown ("k")) {
 
             Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
             RaycastHit hit;
 
         
             if(Physics.Raycast (ray,out hit) && hit.collider.gameObject.name == "BlackTile(Clone)")
             {
                 importScore.Score ();
                 importSound.SoundFXs();
                 correctTouch = true;
 
 
                     grabBlackClonesArray [1].transform.position -= new Vector3 (0.0f, 1.25f, 0.0f);
                     grabBlackClonesArray [0].transform.position -= new Vector3 (0.0f, 1.25f, 0.0f);
                     grabBlackClonesArray [2].transform.position -= new Vector3 (0.0f, 1.25f, 0.0f);
                     grabBlackClonesArray [3].transform.position -= new Vector3 (0.0f, 1.25f, 0.0f);
                     grabBlackClonesArray [4].transform.position -= new Vector3 (0.0f, 1.25f, 0.0f);
                 
         
             
         
             }
 
             else if(Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began) {
                 touchCounter++;
                 if(touchCounter == 1) {
 
                     Application.LoadLevel(2);
                     touchCounter--;
 
 
                 }
 
             }
    }
 
   }
 
     void OnGUI() {
         GUI.matrix = Matrix4x4.TRS(Vector3.zero, Quaternion.identity, new Vector3(4, 2, 1));
         GUI.Label (new Rect (9,125,255,255), (importScorelog));
 
         }
  }

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