OnTriggerEnter not recording value decrease?

Unity Engine
1

I’m trying to make it so when it hits other colliders with matching tags, it will do as follows… and it only does it say 1 out of 4 hits?

using UnityEngine;
using System.Collections;

public class heartSystem : MonoBehaviour {

	public float healthAmount; 
	public GameObject heart; 
	public Transform heartSpawn; 

	public float countDown; 
	public GUIText health; 

	// Use this for initialization
	void Start () {
		countDown = 20; 
		healthAmount = 3; 

	}
	
	// Update is called once per frame
	void Update () {
		countDown -= Time.deltaTime; 

		if (healthAmount <= 0) {

			Time.timeScale = 0.25f; 

				}

		 if (countDown <= 0){

			Instantiate (heart, heartSpawn.position, heartSpawn.rotation); 
			countDown = 20; 
		}

		health.text = "Lives: " + healthAmount; 

		}

	void OnTriggerEnter (Collider other){
	
	
	if (other.tag == "Heart") {
		
		healthAmount += 1; 
	}
	
	if (other.tag == "Asteroid") {
		
		healthAmount -= 1; 
		
		
	}
}
}
2

have you tried using
if (other.gameObject.tag == “”)

instead of just if (other.tag == “”)