Game randomly subtracts 2 lives when it is only supposed to subtract 1

In my game, objects fall towards the bottom of the screen and the player has to shoot them out. In Lives mode, if they pass the bottom of the screen, 1 life is supposed to be subtracted and all other objects one the screen are destroyed to sort of reset and give the player a second.

Every once in awhile it will subtract 2 lives instead of just 1.

This Update checks if an object has gone past the bottom of the screen.

 void Update () {
 
         isColliding = false;
 
         Vector2 pos = transform.position;
 
         pos = new Vector2 (pos.x, pos.y - speedY * Time.deltaTime);
 
 
         transform.position = pos;
 
         Vector2 min = Camera.main.ViewportToWorldPoint(new Vector2 (0,0));
 
         if(transform.position.y < min.y - 0.5){
 
             if(!isFalling){
                 if(ClickType.gameType == 2){
                     gameObject.GetComponent<AudioSource>().clip = oops;
                     gameObject.GetComponent<AudioSource>().Play();
                 }    
                 isFalling = true;
             }
 
             StartCoroutine(OhNo());
         }
 
     }
 

This is what performs when an object does go past the screen

 IEnumerator OhNo(){
         
         yield return new WaitForSeconds(0.8f);
         Destroy(gameObject);
         if(ClickType.gameType == 2){
             GameObject[] fallingShapes = GameObject.FindGameObjectsWithTag("FallingShape");
             foreach(GameObject fS in fallingShapes){
                 GameObject.Destroy(fS);
             }
             Timer.livesRemaining -= 1;
             Debug.Log("Lives are:" + Timer.livesRemaining);
         }
     }

Any and all help would be much appreciated. Thanks very much!