Help with moving instantiated object's transform

Hello guys, this is an edited question. I reread what I originally posted and decided that I need to explain what I need help with better. Okay let me piece this together carefully.

//The black squares are instantiated at start at random from the Top row, to the row just above the Yellow.

//I need the blocks to move down EXACTLY -1.25f on the Y axis. In other words the block will move down 1 space. (They all need to move together).

//Only the black block closest to the yellow will execute this command, the others should not do this until they have reached the y axis of -3.75f.

//The gameobject's name is "BlackTileClone" with a tag of "BlackTile"

//I send a raycast to mouse position with a if statement of "touchcount > 0"

//I've tested various methods like FindGameObjectWithTag and GameObject.name and my results weren't so good. I tried using a foreach loop and it appears that my -1.25 was multiplied by the number of instantiated blocks. (numBlackBlocks * -1.25).

//I know the answer is right in front of my. I feel as though I've stressed myself out to the point that everything is complicated. >.<

Here is the picture of my game.

I have added some code that I feel is very close and precise. I put a lot of effort into commenting out every decision I made.

 using UnityEngine;
 using System.Collections;
 
 public class Movement : MonoBehaviour {
     private bool canexecute;
     private GameObject[] grabBlackClonesArray;
  
     //We created our bool to determine if the cube is at -3.75f
     //We also created the GameObject Array
     
     
     
     void Start()
     {
         //We set the array to have slots 0,1,2,3 (total of 4)
         grabBlackClonesArray = new GameObject[3];
 
         //We debug to see if the position 0 is not null
         Debug.Log (grabBlackClonesArray[0]);
     }
     
     
     
     
     
     void Update() {
 
         //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
         Debug.Log (grabBlackClonesArray[0]);
         //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
         for(int i = 0; i < 1; i++) {
             //With this code the Black Block in slot [1] SHOULD only move EXACTLY 
             //-1.25f from it's CURRENT location. However this isn't true.
             //I get these numbers, far from being exact.
             //X:1.657822 Y:-0.6175802 Z:-13.79006
             //Also somewhere around here is were we would include our bool
             //to check if the block in [1] is in the -3.75 Y position, and if it is it can be executed then moved up top
             //in a random vector (Reusing resources)
             grabBlackClonesArray [1].transform.position = new Vector3 (transform.position.x, transform.position.y -1.25f , transform.position.z);
         }
     }
 }

It appears as though it's because my instantiated objects are placed using Random.Range. The blacktile that I change the vector value of ALWAYS stays in the same place with each game restart. It is no longer random like it should be.