OnMouseDown and OnMouseDrag with RayCast

I've been working on a clone similar to fruit slice and I've been having a problem with onMouseDown and onMouseDrag working 100% correctly. Right now if I click and drag on the screen before it touches an object (e.g. the fruit) it will correctly slice as many objects as I want. It's using a RayCast to figure out whether it has touched the object and then it will change the graphic on the object after it has touched. The problem comes in when I begin my slice on the actual object. It'll change the animation of the object that I initallity touched; however, it won't let me continue to 'slice' any of the other objects. The RayCast seems to stop working after the first object is touched directly until I release the mouse and then re-click another object. Then it goes back into the same pattern, if I don't click the object directly first it'll continue to slice, or if I do touch the object directly it'll only allow the first object to be detected.

Here is the onMouseDrag code that I've been using:

    RaycastHit hit;
    if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit))
    {
        Transform objecthit = hit.transform;
        if (hit.transform.gameObject.tag == "testObject")
        {
            //Change material
        }
    }

I've also included a getMouseButtonDown statement in my Update(), since that was the only way I could get it to at least change the material on the initial click of the object. If I didn't add this in nothing would happen if I clicked the object directly:

  void Update()
     {
         if (Input.GetMouseButtonDown(0))
         {
             RaycastHit hit;
             if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit))
             {
                 Transform objecthit = hit.transform;
                 if (hit.transform.gameObject.tag == "testObject")
                 {
                 //Change Material
                 }
             }
         }
     }

Is there a way to get the RayCast to continue to detect even if the object is touched directly?