Object Pooling Causing Stutter

Hi everyone. I've been working on a game with a space ship that dodges asteroids, and I finally got everything running smoothly on my android device. However, it seems that my game has inexplicably started to hiccup every few seconds. I narrowed down the issues to my object pooling and generator script, but I can't seem to figure out what is causing the lag. Here's hoping a fresh set of eyes will help. I created an entirely new project with all the default unity settings (except of course I changed the platform to Android and changed the bundle ID). In this new project, I have only my generator and object pooling related scripts and as expected, there is a hiccup in the movement every 2-3 seconds. Below are all the relevant scripts. FYI, the rigidbody component of the asteroid prefab is set to "isKinematic."

ObjectPooler.cs - attached to an empty game object.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class ObjectPooler : MonoBehaviour
 {
     public GameObject pooledObject;
     public int poolSize;
 
     private List<GameObject> _pool;
     private Transform _poolTransform;
 
     void Awake()
     {
         // Initialize private variables.
         _pool = new List<GameObject>();    // Initialize the pool list.
         _poolTransform = transform;        // Cache a reference to the pool's transform.
     }
 
     void Start()
     {
         // Initialize the pool by adding some instances of our prefab.
         for( int i = 0; i < poolSize; i++ )
         {
             addToPool();
         }
     }
 
     public GameObject GetPooledObject()
     {
         // Cycle through all of our pooled objects.
         foreach( GameObject go in _pool )
         {
             // If we find an inactive object in our pool...
             if( !go.activeInHierarchy )
             {
                 go.SetActive( true );    // Set the object to active.
                 return( go );            // Return the game object.
             }
         }
 
         // If we didn't find an available object in our pool, instantiate a new one.
         GameObject newObject = addToPool();
         newObject.SetActive( true );
         return( newObject );
     }
 
     private GameObject addToPool()
     {
         GameObject go = Instantiate( pooledObject );
         go.transform.parent = _poolTransform;
         go.SetActive( false );
         _pool.Add( go );
         return( go );
     }
 }
 

Generator.cs - attached to an empty game object.

 using UnityEngine;
 using System.Collections;
 
 public class Generator : MonoBehaviour
 {
     public ObjectPooler asteroidPool;    // The object pooler designed to generate asteroids.
 
     private float _createPosX;    // Horizontal position at which obstacles are generated.
     private float _startDelay;    // Time to wait before starting to generate obstacles.
 
     void Awake()
     {
         // Initialize private variables.
         _createPosX = 15.0f;
         _startDelay = 1.0f;
     }
 
     void Start()
     {
         // Begin the coroutines that generate obstacles.
         StartCoroutine( GenerateAsteroids() );
     }
     
     IEnumerator GenerateAsteroids()
     {
         // Delay generation in the beginning of the game.
         yield return new WaitForSeconds( _startDelay );
 
         // Loop forever.
         while( true )
         {
             // Randomize attributes of our new asteroid.
             float posY = Random.Range( -5.0f, 5.0f );    
             float speed = Random.Range( 3.0f, 5.0f );
             float angVel = Random.Range( -50.0f, 50.0f );
 
             // Select a game object from our object pool and set it to active.
             GameObject newAsteroid = asteroidPool.GetPooledObject();
 
             // Cache references to the new game object's transform and rigidbody components.
             Rigidbody2D rb = newAsteroid.GetComponent<Rigidbody2D>();
             Transform newTransform = newAsteroid.transform;
 
             // Apply the appropriate speed, position, etc.
             newTransform.position = new Vector2( _createPosX, posY );
             rb.velocity = Vector2.left * speed;
             rb.angularVelocity = angVel;
 
             // Wait a while before generating a new asteroid;
             yield return new WaitForSeconds( 2.2f );
         }
     }
 }
 

DestroyArea.cs - attached to an empty game object with a box collider sitting at the edge of the screen.

 using UnityEngine;
 using System.Collections;
 
 public class DestroyArea : MonoBehaviour
 {
     void OnTriggerEnter2D( Collider2D col )
     {
         col.gameObject.SetActive( false );
     }
 }