I believe a lot of the floral elements similar to the vector stock set are from public domain old books etc. (not necessarily that specific one, but that style)
There are some massive scanned libraries of very old books online, I wouldn't be surprised if some of the artists are using those (Gutenberg etc.)
The other two I think are just created from scratch by designers.
A heck of a lot of these sets are just rip offs from other micro stock contributors (again not necessarily the specific ones linked to).
At one point there were hundreds of copies of AKaiser's work flooding the market every day, because she was one of the first to come up with high quality sets in that style.