Im creating a dr.mario style game however code its not functioning correctly

Im creating a dr.mario style game however code its not functioning correctly . so i started with creating a tetris game however im getting stuck on how to incorporate match 4 instead of delete line and how to split the game object for it to drop the leftovers till it hits something or the ground

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class pill : MonoBehaviour
 {
     private float pTime;
     public float fallTime = 0.8f;
     public static int height = 20;
     public static int width = 8;
     public Vector3 rotationPoint;
     private static Transform[,] grid = new Transform[width, height];
     // Start is called before the first frame update
     void Start()
     {
         
     }
 
     void CheckForLines()
     {
         for (int i = height -1; i >= 0; i--)
         {
             if(HasLine(i))
             {
                 DeleteLine(i);
                 RowDown(i);
             }
         }
     }
 
     bool HasLine(int i)
     {
 
         for (int j = 0;  j < width; j++)
         {        
             if (grid[j, i] == null){
                 return false;
             }
             
         }
         
         return true;
 
     }
 
     void DeleteLine(int i)
     {
         for (int j = 0; j < width; j++)
         {
             Destroy(grid[j,i].gameObject);
             grid[j,i ] = null; 
         }
     }
 
     void RowDown(int i )
     {
         for(int y = i; y < height;  y++)
         {
             for (int j = 0; j < width; j++)
             {
                 if(grid[j,y] != null)
                 {
                     grid[j, y - 1] = grid[j, y];
                     grid[j, y] = null;
                     grid[j, y - i].transform.position -= new Vector3(0,1,0);
                 }
             }
         }
     }
 
     void AddToGrid()
     {
         foreach (Transform children in transform)
         {
             int roundedX = Mathf.RoundToInt(children.transform.position.x);   
             int roundedY = Mathf.RoundToInt(children.transform.position.y);  
             grid[roundedX, roundedY] = children; 
         }
     }
 
     // Update is called once per frame
     void Update()
     {
         if (Input.GetKeyDown(KeyCode.LeftArrow))
         {
             transform.position += new Vector3(-1, 0, 0);
 
             if(!ValidMove())
             {
                 transform.position -= new Vector3(-1, 0, 0);
             }       
         } 
 
         else if (Input.GetKeyDown(KeyCode.RightArrow))
         {
             transform.position += new Vector3(1, 0, 0);
 
             if(!ValidMove())
             {
                 transform.position -= new Vector3(1, 0, 0);
             }        
         }
 
         else if (Input.GetKeyDown(KeyCode.UpArrow))
         {
             transform.RotateAround(transform.TransformPoint(rotationPoint), new Vector3(0,0,1), 90);
             if(!ValidMove())
             {
                 transform.RotateAround(transform.TransformPoint(rotationPoint), new Vector3(0,0,1), -90);
             } 
         }
 
         if(Time.time - pTime > (Input.GetKey(KeyCode.DownArrow) ? fallTime / 10 : fallTime))
         {
             transform.position += new Vector3(0, -1, 0);
 
             if(!ValidMove())
             {
                 transform.position -= new Vector3(0, -1, 0);
                 AddToGrid();
                 CheckForLines();
                 this.enabled = false;
                 FindObjectOfType<spawner>().NewPill();
             }        
 
             pTime = Time.time;          
         }
     }
 
     bool ValidMove()
     {
         foreach (Transform children in transform)
         {
             int roundedX = Mathf.RoundToInt(children.transform.position.x);   
             int roundedY = Mathf.RoundToInt(children.transform.position.y);  
 
             if(roundedX < 0 || roundedX >= width || roundedY < 0 || roundedY >= height)
             {
                 return false;
             }
             
             if(grid[roundedX, roundedY] != null)
             {
                 return false;
             }
         }
 
         return true;
     }
 }