Touch point not detected correctly on GUI Texture

My buttons are working correctly. The texture swaps when i touch the texture and when I let go. However, the problem is it doesn't detect the accurately.

When I touch a little below the button, it still works when I don't want it to.

My code is below. I do think I'm on the right tracks.

 var targetGui : GUITexture;
 var hoverTex : Texture2D;
 var normalTex : Texture2D;
 
 function Start () {
 
 }
 
 function Update(){
     if (Input.touchCount == 1)
     {
         var touch: Touch = Input.touches[0]; 
  
         if(touch.phase == TouchPhase.Began && guiTexture.HitTest(touch.position))
                {
                targetGui.texture = hoverTex;
             //Application.LoadLevel("Level 1");
                } 
         if(touch.phase == TouchPhase.Ended && guiTexture.HitTest(touch.position))
                {    
             targetGui.texture = normalTex;
             }
     }
 }