GUI Performance & Texture Atlasing

I've been developing my RPG, and have had awful performance with the GUI System. It really lowers my FPS, and I'm trying to find a way to improve the performance but I have a few questions.

GUI Off:

GUI On:

I was looking into reducing draw calls by using a texture atlas. I have the same texture repeated 10 times in a row right next to eachother (The buttons on the bottom right of my GUI) and it still uses 10 draw calls, rather than 1. Does texture atlasing actually reduce the draw calls and improve the performance of the GUI?

I am not drawing very much on the screen, 10 buttons with 10 images on the buttons, 3 images for the minimap, and about 5 images for the chatbox and a few labels. I think that's very little to be drawn on the screen, and it's really destroying my FPS. What could be the cause?

Here is a little bit of code drawing the buttons on the bottom right.

         //Draws tabs
         private void DrawTabs ()
         {
                 GUI.DrawTexture (new Rect (Screen.width - 1, Screen.height - Config.TAB_BUTTON_HEIGHT, 1, Config.TAB_BUTTON_HEIGHT), tabBackground [3]);
                 int activeTabIndex = 0;
                 for (int i = 0; i < Config.MAX_TABS; i++) {    
                         //Checks to see if tab is enabled
                         if (!tabSystem.isTabEnabled (i))
                                 continue;
             
                         int x = Screen.width - ((activeTabIndex + 1) * Config.TAB_BUTTON_WIDTH) - 1;
                         int y = Screen.height - Config.TAB_BUTTON_HEIGHT;
                         Rect rect = new Rect (x, y, Config.TAB_BUTTON_WIDTH, Config.TAB_BUTTON_HEIGHT);
                         GUIButtonSystem.TextureButtonHover2 (rect, tabBackground [0], tabBackground [1], tabSystem.getCurrentTab () != i ? "Open Tab" : "Close Tab", "", ClickTab, i);
                         if (tabSystem.getCurrentTab () == i) {
                                 GUI.DrawTexture (rect, tabBackground [2]);
                         }
                         if (tabIcons [(i * 2)] != null && tabIcons [(i * 2) + 1] != null)
                         if (tabSystem.getCurrentTab () != i)
                                 GUIButtonSystem.TextureHover (rect, tabIcons [(i * 2)], tabIcons [(i * 2) + 1]);
                         else
                                 GUI.DrawTexture (new Rect (rect.x + 2, rect.y + 2, rect.width - 4, rect.height - 4), tabIcons [(i * 2)]);
                         activeTabIndex++;
                 }
         }

     public static void TextureButtonHover2 (Rect rect, Texture buttonTexture, Texture buttonHoverTexture, string action, string name, RightClickHandler.menuActionDelegate del, int id)
     {
         bool inButton = rect.Contains (MousePositionHandler.getMousePositionVerticalSwitch ());
         GUI.DrawTexture (rect, inButton ? buttonHoverTexture : buttonTexture);
         if(inButton) {
             RightClickHandler.addMenuItem(action, name, del, id, 0);
         }
     }

As you can see, I'm not doing anything too crazy with the code. Why is my performance so bad? All help is really appreciated.