Replacement for Raycast / FPS drops problem

Well, I have an extremely simple game, with blocks and a character that hits them and destroys the block. I use Raycast to find the blocks, like this (raycastOrigin is a transform right in front of the character): if (Physics.Raycast(raycastOrigin.position, raycastOrigin.forward, out hit, range, blocksLayer)) {...}

While I'm hitting blocks the fps drops a lot, and on the profiler window Active Rigidbodies and Number of Contacts were really high, so I supposed the problems were with Raycasts, since I just learned they are really expensive.

I tried to do some things (read below) and it got just a little better, but fps is still dropping too much, as you can see here: http://imgur.com/7Ew3vGy.

What I did: I put all the blocks that can be hit in a single layer and I start coroutines to make the raycasts and deal with collisions. I tried other things like changing Update to FixedUpdate, but no changes.

I don't know what to do now, I started to learn about Unity recently and don't have the necessary knowledge to handle this properly. Is there a way to fix my problem or to use a replacement for Raycast that doesn't make fps drop?

My actual code where I am Raycasting:

 void Update () {

     time = time + Time.deltaTime;

     if (Input.GetButton("Fire1") && time > nextFire)
     {
         nextFire = time + fireDelta;

         StartCoroutine(FindBlockRaycasting());

         nextFire = nextFire - time;
         time = 0.0F;
     }
 }

 private IEnumerator FindBlockRaycasting()
 {
     if (Physics.Raycast(raycastOrigin.position, raycastOrigin.forward, out hit, range, blocksLayer))
     {
         target = hit.collider.gameObject;
         warn = target.tag;
         if (target.tag == "Destroyable")
         {
             animator.Play("HitWithArm", -1, 0F);
             target.GetComponent<DestroyWhenHit>().GetHit();
         }
     }

     yield return new WaitForSeconds(0);
     }