Problems with Custom Tool Tip Generation

I am currently having problems generating custom windows to appear when hovering over an item in my inventory. I am using a self modified version of Brackeys Inventory System.

All works fine, if i hover over the objects the window appears on my cursor as expected. But when i take away my cursor from any icon it still persists.

The Code for this as follows:

 //Drawing the Inventory window
 function OnGUI()
 {
     GUI.skin = invSkin;
     
     if(itemBeingDragged != null) //If we are dragging an Item, draw the button on top:
     {
         GUI.depth = 3;
         GUI.Button(Rect(draggedItemPosition.x,draggedItemPosition.y,draggedItemSize.x,draggedItemSize.y),itemBeingDragged.itemIcon);
         GUI.depth = 0;
     }
     
     //If the inventory is opened up we create the Inventory window:
     if(DisplayWindow)
     {
         mouse = new Vector2(Input.mousePosition.x, Screen.height - Input.mousePosition.y);
         WepHand.CanUseInventory = false;
         CameraScript.LockCamera();
         CameraUnlocked = false;
         windowRect = GUI.Window (windowID, windowRect, SetUpDisplayWindow, WindowName);    
 
     }
     else
     {
         if(!CameraUnlocked)
         {
             CameraScript.UnlockCamera();
             CameraUnlocked = true;
         }
         
         WepHand.CanUseInventory = true;
     }
     
     GUI.skin = ToolTipSkin;
     if(HoverItem != null)
     {
         ToolTipRectangle = GUI.Window(99, ToolTipRectangle, ToolTipSetup, "");
     }
     
 }
 
 function SetUpDisplayWindow(windowID:int)
 {
     GUI.skin = invSkin; //Use the invSkin
     var MaxSpace : int = InventoryObj.GetComponent(InvStorage).MaxContent;
     var SpaceTaken : int = InventoryObj.GetComponent(InvStorage).Contents.Length;
     GUI.Label(Rect(12, 5,100,100),  (MaxSpace - SpaceTaken) +  " / " +   MaxSpace );
     
     if (canBeDragged == true)
     {
         GUI.DragWindow (Rect (0,0, 10000, 30));  //the window to be able to be dragged
     }
 
     var currentX = 0 + Offset.x; //Where to put the first items.
     var currentY = 18 + Offset.y; //Im setting the start y position to 18 to give room for the title bar on the window.
 
     for(var i:Transform in UpdatedList) //Start a loop for whats in our list.
     {
         //Get the items script
         var item=i.GetComponent(Item);
         //Create a button for this instance
         ButtonRect = new Rect(currentX,currentY,itemIconSize.x,itemIconSize.y);
         
         // if the player clicks this button, add the item to their inventory
         if (GUI.Button(ButtonRect, item.itemIcon))
         {
             if(PlayerInv.Contents.Length < PlayerInv.MaxContent)
             {
                 item.TransferToPlayer(i);
             }
         }
         
         //if hovering over the item, trigger an window to open with info on the object
         if(ButtonRect.Contains(new Vector2(mouse.x - windowRect.x, mouse.y - windowRect.y))) 
         {
             HoverItem = item;
         }
         
         //If its stackable, display the ammount in the stack
         if(item.stackable) //If the item can be stacked:
         {
             GUI.Label(Rect(currentX, currentY, itemIconSize.x, itemIconSize.y), "" + item.stack, "Stacks"); //Showing the number (if stacked).
         }
         
         //Space the items out in the display.
         currentX += itemIconSize.x;
         if(currentX + itemIconSize.x + Offset.x > windowSize.x) //Make new row
         {
             currentX=Offset.x; //Move it back to its startpoint wich is 0 + offsetX.
             currentY+=itemIconSize.y; //Move it down a row.
             if(currentY + itemIconSize.y + Offset.y > windowSize.y) //If there are no more room for rows we exit the loop.
             {
                 return;
             }
         }
         
     }
 
 }
 
 
 function ToolTipSetup(windowID : int)
 {
     ToolTipRectangle.position = mouse;
 
 }
 

Annoying, i thought if i added in an else statement to the ButtonBox.Contains it would fix it, but it only makes things worse. It only shows a tooltip for the final item, but atleast it dissapears.

         //if hovering over the item, trigger an window to open with info on the object
         if(ButtonRect.Contains(new Vector2(mouse.x - windowRect.x, mouse.y - windowRect.y))) 
         {
             HoverItem = item;
         }
         else
         {
             HoverItem = null;
         }

It appears to me its due to the type of loop that is used in the procedural generation of the inventory icons...

Any ideas on the best way to achieve what i am trying to do?