If you didn't get them from differant breeders, then I would wait a month to make sure they are healthy then breed them in QT. If they are from differant breeders then they should technically be in differant QT areas, if they are in the same area and you use the same utensils for both ( ie; feeding tongs, water bowls) then the chance of cross contamination is the same as if you were breeding them. I have never gotten a pair of snakes that were both breeder size in QT before, but if I did then I would consider breeding them in Qt after an intial observation period.