It doesn't add points

Hello, I am doing the Flappy Bird script and I'm actually finished but I have one problem which is that when I'm going through the first column, I get a point but when I go through any other columns it doesn't add points so the points will stay on 1.

ColumnPool script:

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

public class ColumnPool : MonoBehaviour { public int columnPoolSize = 5; public GameObject columnPrefab; public float spawnRate = 4f; public float columnMin = -1f; public float columnMax = 3.5f;

 private GameObject[] column;
 private Vector2 objectPoolPosition = new Vector2 (-15, -25f);
 private float timeSinceLastSpawned;
 private float spawnXPosition = 10f;
 private int currentColumn = 0;

 // Use this for initialization
 void Start ()
 {
     column = new GameObject[columnPoolSize];
     for (int i = 0; i < columnPoolSize; i++)
     {
         column[i] = (GameObject)Instantiate (columnPrefab, objectPoolPosition, Quaternion.identity);
     }
 }
 

 // Update is called once per frame
 void Update ()
 {
     timeSinceLastSpawned += Time.deltaTime;

     if (GameController.instance.gameOver == false && timeSinceLastSpawned >= spawnRate)
     {
         timeSinceLastSpawned = 0;
         float spawnYPosition = Random.Range (columnMin, columnMax);
         column [currentColumn].transform.position = new Vector2 (spawnXPosition, spawnYPosition);
         currentColumn++; 
         if (currentColumn >= columnPoolSize)
         {
             currentColumn = 0;
         }
     }
 }

}

Column script:

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

public class Column : MonoBehaviour { private void OnTriggerEnter2D (Collider2D other) { if (other.GetComponent () != null) { GameController.instance.BirdScored (); } } }