Does all you products are up to date with virus definitions ( not product updates)
Norton 360 will detect the same ones that SEP is detecting and Norton 360 will detect more than sep as its a home product and Heristic scanning is more intense.
The only reason i think they are getting detected would be the threats you have are news and it just got detected by the latest set of virus definitions that were not there in norton 360.
Anyways what you have seen is very rare so there is nothing to be worried about just make sure you are up-to-date on virus definitions