You did not mention if these are connecting flights or separate ones, or if you booked a light or a standard fare.
If they are connecting fligths I believe DL will give you the SM allowance on DL, so if you booked light you would get one bag and if you booked standard you would get two.
If they are separate flights then I would suggest you check your VS reservation on the VS site. If it says light you won't get a bag, if it says classic you would get one. In this case the DoT regulation about the first marketing carrier may cover you but I'm not sure as I'm not too familiar with it.