Function to locate game object with smaller distance to target makes the game lag - UnityScript

Hi there!

So, I've done this function so the script would discover which of a group of certain gameObjects (each representing a weapon) would be closer to the target. However, every time I fire the weapon, the game begins to lag (FPS drop from 63 to 0.3). Is there any recomendation to improve it? Here it is:

 function CheckClosestWeapon  (weaponTag : String, parent : Transform) : GameObject
 {
     var closest : GameObject;
     for (var weapon_go : GameObject in GameObject.FindGameObjectsWithTag(weaponTag))
     {
     
         if (closest != null)
         {
             if (weapon_go.transform.parent.parent.transform == parent)
             {
             
                 var distance1 = Vector3.Distance(weapon_go.transform.position, target.position);
                 var distance2 = Vector3.Distance(closest.transform.position, target.position);
                 
                 if (distance1 < distance2)
                 {
                     closest = weapon_go;
                 }
             
             
             
             }
         
         
         }
         else
         {
             if (weapon_go.transform.parent.parent.transform == parent)
             {    
                 closest = weapon_go;
             }
         
         }
     }
     return closest;
 
 
 
 }

Thanks in advance...