There is not, to my knowledge, a central database for "bath salts"/"plant food". EcstacyData and Pillreports sometimes have test results from bath salts however, and there have been studies in the scientific literature that have shown that even within the same "brand" there can be considerable variance in active ingredients. Put plainly, every bag is different.
So in short, there is really no way aside from lab tests to tell if your "bath salts" are drugs or not. Even if you provide a name/purchase date, that means very little because there are numerous fakers out there.
It's a reasonable question, but like another poster said, all we can do is speculate so we can't entertain the notion.