Or we could say that the Son'a were master chemists, were contracted to do KW for the Dominion, and after the war discovered new and profitable narcotic uses for the stuff. Or then they modified the stuff, so that there now exists standard KW, narcotic KW, stimulating KW, and perhaps also Ketracel Green, Ketracel Yellow and Ketracel Light for the aware and discriminating consumer.
Timo Saloniemi
Ketracel Green is made of B'aku. IT'S MADE OF B'AKU!
I'll bow to your superior wisdom on the timeframe, although they do mention Worf is still stationed on DS9, right?
As an alternative, if we want to speculate it did take place during the war, there might have been two Son'a factions, one led by Rufao the B'aku exile and another, proper Son'a homeworld and empire, from which the original B'aku settlers hailed. Hey, maybe the other faction was even interesting!