How to delete GameobjectS on collision??

Hey guys, this question is anwered a thousand times,but i cant handle it. What im doing right now is building an Tetris like 3D Game. The Problem now is,that i cant build a simple row or something like this and when its filled just delete it. My first idea was to look up how many Blocks can the platform on which the blocks are placed take. But this idea was fast thrown away,cause the blocks vary in their sizes. So what im searching for now is how i can detect the number of blocks lying on the platform and second how can i destroy multiple blocks(gameobjects) lying on that platform at the same time because this is not working ,too.Unity just destroys teh last block placed nothing more if the counter for the blocks hits the limit. I gonna post my code here now. You can irgnore bool grabbed as its inherited from another class

Thanks for helping!!

using UnityEngine; using System.Collections;

public class ROwsystem : MonoBehaviour { public static bool grabbed; public int filledrow; public GameObject g; public Collider col; // Use this for initialization void Start () {

     col = GetComponent<Collider> ();
 }
 
 // Update is called once per frame
 void Update () {
 

     if (filledrow ==5) {
         
         
         filledrow = 0;
         Destroy(GameObject.FindWithTag("row1"));
         
     }
     

 }

void OnCollisionEnter(Collision other) { if(other.gameObject.tag=="block") filledrow ++;

     other.gameObject.tag = "row1";

 
     

         
         



 }
 void OnCollisionExit(Collision other)
 {
     filledrow--;
     
     
 }
 void OnCollisionStay(Collision other)
 {
     other.gameObject.tag = "row1";
     
 
 
 }




 void OnGUI()
 {

     GUI.Label (new Rect (150, 0, 100, 20), "" + filledrow ); 
 }

}