Hello Kalyan,
I would assume on the Combo Boxes that it is a simple configuration of the items to make sure that they are either all linking back to left or right - depending on how you design it, or you can also use another grid layout to make sure they are all organized properly.
On the background I assume you refer to the white background just becoming larger - that is what I would call "expected" as your combobox component did grow and it comes with a background color.
regards
Ingo Hilgefort, Visual BI