Change Texture From World Position Amplify Shader

I Recenly wrote a shader which change the texture of a gameobject form world position it is working fine on PC , Android , Mac but not working on IOS. Here is a screen shot of shader:

https://flic.kr/p/2m32nW6

 if (Input.GetMouseButtonDown(0))
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             RaycastHit raycastHit;
             if (Physics.Raycast(ray,out raycastHit,1000.0f))
             {
                 material_hit = raycastHit.transform.gameObject.GetComponent<Renderer>().sharedMaterial;
                 //Get Texture
                 material_hit.SetTexture("_NormalMap1", material_hit.GetTexture("_NormalMap2"));
                 //Set Texture
                 normalIndex++;
                 normalIndex = normalIndex % 2;
                 material_hit.SetTexture("_NormalMap2", normals[normalIndex]);
                 //Get Color
                 material_hit.SetColor("_Diffuse1Color", material_hit.GetColor("_Diffuse2Color"));
                 //Set Color
                 material_hit.SetColor("_Diffuse2Color", Random.ColorHSV());
                 //material_hit.SetFloat("_speed", 1.9f);
                 material_hit.SetVector("_postion", raycastHit.point);
                 material_hit.SetFloat("_start_time", Time.timeSinceLevelLoad);
             }
                 //
         }