Level spawning statement help

So in my script i have a level spawner that spawns 10 enemies and the level increases. On Level 4 there is a sub-boss that appears, in the script i have a trigger that can control to turn the spawner off or on. So in this instance i turn it off so the player is fighting the boss only and not the minions.

Now my question is I need help making a statement where if the boss dies turn the level thing back on. It would be great if you could link me, or even tell me the code.

here is 2 scripts one that spawns the subboss and one that destroys it, keep in mind if i remove "IsON=False" it floods the screen with enemies

script 1

 var isON: boolean = true;
 var Enemyred: Transform;
 
 function Update () {
 
 if (level == 4 && isON == true){
         isON = false;
         Instantiate(Enemyred, Vector3(0,8,2), Quaternion.identity);
         }
 }

script 2 which destroys the ship when the laser collides with it

 function OnCollisionEnter(col : Collision){
 
 if(col.gameObject.tag == "Enemy_Red"){
         Destroy(gameObject);
         if (enemyred == null){
                 enemyred = GameObject.FindWithTag("Enemy_Red").GetComponent(Enemy_Red);
                 }
         enemyred.health -= 50;
         Destroy(gameObject);
                 
     }

Two thumbs up if you help thank you