Parallax moving with camera

[UEG_Productions]

I have the following code for a background that moves with the mouse:

if(room == rm_Title_914){
var cam_x, cam_y;
cam_x = mouse_x-room_width/1.5;
cam_y = mouse_y-room_width/3.5;

#region ENEMY LAYER -6
if (layer_exists("BG_Color"))
{
    layer_x("BG_Color",cam_x/-10);
}

if (layer_exists("BG_Color"))
{
    layer_y("BG_Color",cam_y/-10);
}
#endregion
}

I have an instance layer with 2 objects that I want to apply this effect to. I am not sure how I would be able to do this with an instance layer.

The objects I have on that layer are rotating: