Help with camera movement using mobile input

I have this script that is attached to my camera. It makes the camera navigate around a specified GameObject. The only problem I have is, it can only make the camera orbit on the X axis when I drag from either left or right, I want to also be able to orbit on the Y axis when I drag up/down.

Here's the code I'm working on:

     public float tumbleSensitivity = 0.3f;        //NB. This value should be adjusted until a natural result is achieved. It affects the amount the camera will tumble around the object as a swipe takes place.
     public Transform pivotPoint;                //this should be the location the camera tumbles around
     public bool naturalMotion = true;            //this determines whether a left swipe will make the camera tumble clockwise or anticlockwise around the object
     
     private GameObject camParent;                //this will be the rotating parent to which the camera is attached. Rotating this object will have the effect of making the camera a specified location.
     private Vector2 oldInputPosition;            //records the position of the finger last update
     
     void Start ()
     {
         Transform originalParent = transform.parent;            //check if this camera already has a parent
         camParent = new GameObject ("camParent");                //create a new gameObject
         camParent.transform.position = pivotPoint.position;        //place the new gameObject at pivotPoint location
         transform.parent = camParent.transform;                    //make this camera a child of the new gameObject
         camParent.transform.parent = originalParent;            //make the new gameobject a child of the original camera parent if it had one
     }
     
     // Update is called once per frame
     void Update ()
     {
 
         //TOUCH
         
         if (Input.touchCount > 0)
         {
             foreach (Touch touch in Input.touches)
             {
                 if (touch.phase == TouchPhase.Began && touch.fingerId == 0)
                 {
                     oldInputPosition = touch.position;
                 }
                 if (touch.phase == TouchPhase.Moved || touch.phase == TouchPhase.Stationary)
                 {
                     if (touch.fingerId == 0)
                     {
                         float xDif = touch.position.x - oldInputPosition.x;    //this calculates the horizontal distance between the current finger location and the location last frame.
                         float yDif = touch.position.y - oldInputPosition.y;
                         if (!naturalMotion){xDif *= -1;yDif *= +1;}
                         if (xDif != 0){camParent.transform.Rotate (Vector3.up * xDif * tumbleSensitivity);}
                         if (yDif != 0){camParent.transform.Rotate (Vector3.right * yDif * tumbleSensitivity);}
                         oldInputPosition = touch.position;
                     }
                 }
                 if (touch.phase == TouchPhase.Ended && touch.fingerId == 0)
                 {
                     oldInputPosition = touch.position;
                 }
             }
         }