Retina specific framerate drop on specific function

I'm working on a game that long story short involves a bunch of cubes flying around. Your player can destroy these cubes at certain intervals, causing them to "blow up", which is basically just instantiating an empty object containing 8 cube objects, (about 150tris each with mobile textures) they don't contain scripts only colliders and rigidbodies.

When running the game on a 1st gen iPad Mini the problem never happens and the framerate stays solid at 60fps. Only on the retina Mini will it bog down to 30fps if you blow up three or more cubes in close succession (0.5-1 second gap) and for the love of god I cannot figure out why. Here is the method that is called when the collision happens. Please let me know if I have something clearly wrong that could be causing such an issue on a current gen retina device.

Additionally, if you'd like more info/example I'd be happy to provide it. Thank you.

  function enemyClusterExplode()
  {
     audioMan.PlayCubeExplode(); //play sfx
     Destroy(this.gameObject);

     //instantiate at pos/rot of enemy cube
     var cubeCluster : Rigidbody = Instantiate(enemyCluster, transform.position, transform.rotation);
     cubeCluster.transform.localScale = gameObject.transform.localScale;

     //give the cluster an explosive force
     var explosionPos : Vector3 = transform.position;
     var colliders : Collider[] = Physics.OverlapSphere (explosionPos, explodeRadius);
     for (var hit : Collider in colliders)
     {
         if(!hit)
             continue;
         
         if(hit.rigidbody)
         hit.rigidbody.AddExplosionForce(explodePower, explosionPos, explodeRadius, 0.3);
     }
 }

UPDATE: I changed the instantiate call above to nested objects that simply get turned on/off when collision happens. Still getting the same issue when you hit 3+ cubes close together in time. I'll have to shift my attention elsewhere as this doesn't look like the problem.

At time of slowdown the stats are showing about 6.5k tris in the scene and between 20-35 draw calls happening. I'm still absolutely confused why this is only occurring on retina hardware…

 function enemyClusterExplode()
 {
     audioMan.PlayCubeExplode();
     cubeCluster.SetActive(true);
     cubeCluster.transform.parent = null;
     //give the cluster an explosive force
     var explosionPos : Vector3 = transform.position;
     var colliders : Collider[] = Physics.OverlapSphere (explosionPos, explodeRadius);
     for (var hit : Collider in colliders)
     {
         if(!hit)
             continue;
         
         if(hit.rigidbody)
         hit.rigidbody.AddExplosionForce(explodePower, explosionPos, explodeRadius, 0.3);
     }
     enemySpawnRef.maxRespawnTime -= 0.009f;
     enemySpawnRef.launchSpeed += 0.01f;
     this.gameObject.SetActive(false);
 }