Resource counter doesn't reset on each iteration

The codes is supposed to add the value of addscore(default 10) to the score every count. The addscore however is changed based on the number of gameobjects with a certain tag, therefore changing amount added to the score. but for some reason, when the tagged objects in question are destroyed, the counter doesn't reset. Do you know what I need to change?

 using UnityEngine;
 using System.Collections;
 
 public class resourceGUI : MonoBehaviour {
     private float score = 0;
     public float addscore;
     private GameObject tax;
     
     // Use this for initialization
     void Start () {
     InvokeRepeating("EachSecond", 0, 1);
     }
     
     // Update is called once per frame
     void Update () {
     GameObject[] tax;    
     tax = GameObject.FindGameObjectsWithTag("soldier");
     addscore=Mathf.Max(0, 10-tax.Length);
 
     }
     void EachSecond(){
     score=score+addscore;    
     }
     void OnGUI(){
         GUI.Box(new Rect(10,10,100,20), score.ToString());
         
     }
 }