Hi Saurabh,
I think this is due to how ShopperPress is updating your products, not Datafeedr.
For example, the watch you linked to above is not in your "Datafeedr" store.
http://shop.yellowpost.com.au/store/...well%20Digital
But other watches are in your Datafeedr store:
http://shop.yellowpost.com.au/store/...Classic%20Mesh
You will need to ask the ShopperPress team how to delete the old products.
Eric