FPS Slowly reduces over time with multi-object pool

I have two turret types in my game, a missile turret and a machine gun turret. They fire missiles and bullets respectively. The bullets have a trail renderer attached, the missile object has a particle trail and spawns an explosion on collision.

I've created a multi-object object pool to go easy on the multiple Instantiate/Destroy calls I would have to make with lots of projectiles.

Here's my object pool script: using UnityEngine; using System.Collections; using System.Collections.Generic;

 public class ObjectPool : MonoBehaviour {
 
     public static ObjectPool instance;
 
     public GameObject[] objectPrefabs;
     public int defaultPoolSize = 40;
 
     private Dictionary<string, List<GameObject>> objectPool;
     protected GameObject containerObject;
     
     void Awake(){
         instance = this;
     }
 
     void Start(){
         objectPool = new Dictionary<string, List<GameObject>> ();
         containerObject = new GameObject ("ObjectPool");
 
         foreach (GameObject obj in objectPrefabs) {
 
             List<GameObject> objects = new List<GameObject>();
 
             for(int i = 0; i < defaultPoolSize; i++){
                 GameObject newObj = Instantiate(obj);
                 newObj.transform.parent = containerObject.transform;
                 newObj.SetActive(false);
                 objects.Add(newObj);
             }
 
             objectPool.Add(obj.name, objects);
         }
     }
 
     public GameObject GetPooledObject(string name){
         List<GameObject> objs =  objectPool[name];
 
         foreach (GameObject obj in objs) {
             if(!obj.activeInHierarchy){
                 return obj;
             }
         }
 
         foreach (GameObject currentObj in objectPrefabs) {
             if(currentObj.name == name){
                 GameObject newObj = Instantiate(currentObj);
                 newObj.transform.parent = containerObject.transform;
                 newObj.SetActive(false);
                 objectPool[name].Add(newObj);
                 return newObj;
             }
         }
 
         return null;
     }
 
 }

Bullets and missiles have the following script attached:

Bullets:

 using UnityEngine;
 using System.Collections;
 
 public class BulletController : MonoBehaviour {
 
     public float speed = 25f;
     public float life = 5f;
     
     public ParticleSystem bulletHit;
     
     private Rigidbody rb;
     private TrailRenderer trailRenderer;
     private MeshRenderer mesh;
 
     void Awake(){
         rb = GetComponent<Rigidbody> ();
         trailRenderer = GetComponent<TrailRenderer> ();
         mesh = GetComponent<MeshRenderer> ();
     }
 
     private void OnEnable(){
         mesh.enabled = true;
         trailRenderer.enabled = true;
         rb.velocity = speed * transform.forward;
         Invoke ("Remove", life);
     }
     
     private void OnDisable(){
         CancelInvoke ();
     }
 
     private void Remove(){
         transform.rotation = Quaternion.identity;
         trailRenderer.enabled = false;
         mesh.enabled = false;
         rb.velocity = Vector3.zero;
         rb.angularVelocity = Vector3.zero;
         transform.position = transform.parent.position;
         Invoke ("WaitTime", 0.5f);
     }
 
     private void OnCollisionEnter(Collision other){
         Remove ();
     }
     
     private void WaitTime(){
         gameObject.SetActive (false);
     }
 }
 

Missiles:

 using UnityEngine;
 using System.Collections;
 
 public class MissileController : MonoBehaviour {
 
     public float speed = 30f;
     public float turnSpeed = 15f;
     public float life = 4f;
     public string explosionName;
 
     [HideInInspector]
     public Transform target;
 
     private ParticleSystem missileTrail;
     private float particleEmissionRate;
     private bool alive;
     private Rigidbody rb;
     private Light light;
     private MeshRenderer mesh;
 
     void Awake(){
         mesh = GetComponent<MeshRenderer> ();
         light = GetComponentInChildren<Light> ();
         rb = GetComponent<Rigidbody> ();
         missileTrail = GetComponentInChildren<ParticleSystem> ();
         particleEmissionRate = missileTrail.emissionRate;
     }
 
     private void OnEnable(){
         rb.isKinematic = false;
         mesh.enabled = true;
         light.enabled = true;
         alive = true;
         missileTrail.emissionRate = particleEmissionRate;
         missileTrail.transform.position = transform.position;
         missileTrail.transform.parent = transform;
         Invoke ("Remove", life);
     }
 
     private void OnDisable(){
         CancelInvoke ();
     }
 
     private void Remove(){
         target = null;
         mesh.enabled = false;
         light.enabled = false;
         alive = false;
         missileTrail.emissionRate = 0;
         transform.position = transform.parent.position;
         rb.isKinematic = true;
     }
 
     private void WaitForTrail(){
         gameObject.SetActive (false);
     }
 
     private void OnCollisionEnter(Collision other){
         GameObject explosion = ObjectPool.instance.GetPooledObject ("Explosion");
         explosion.transform.position = transform.position;
         explosion.SetActive (true);
 
         Remove ();
         Invoke ("WaitForTrail", 2f);    
     }
 
     void FixedUpdate () {
         if (target && alive) {
             transform.Translate(Vector3.forward * speed * Time.deltaTime);
             Quaternion rot = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(target.position - transform.position), turnSpeed * Time.deltaTime);
             transform.rotation = rot;
         }
     }
 }

Bullets and missiles are instantiated with the following lines:

 GameObject bullet = ObjectPool.instance.GetPooledObject("Bullet");
 bullet.transform.position = t.position;
 bullet.transform.rotation = Quaternion.LookRotation(dir);
 bullet.SetActive(true);

The issue I'm getting is that my fps lowers over time, in the Unity editor and standalone .exe file. I've looked at the profiler and the WaitTime() & WaitForTrail() methods cause occasional spikes which seem to increase in duration over time. The overdraw seems to be high as well.