In general it is not a good practice to initialize Kendo UI widgets using it's class names, as it might cause some discrepancies.
In your case the problem comes from the fact that when initialized the DropDownList creates a span element with the same class name as the input element. So you have total of 6 elements in your $.each() statement and you need only the input elements nested in the span, that were used to initialize the widget.
I would suggest you to take the whole collection and use only the elements that you need and then set their dataSource. Please check the following example:
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI