West Poison Au Yeung Fung was the undisputed master of animal-based poisons in his generation: snake poison, scorpion poison, arachnid (i.e. spider) poison, insect poison, centipede poison...he knew his way around these like nobody else on the planet.
But what about plant- and fungus-based poisons? Were those in his repertoire? Could he have figured out how, for example, the Passion Flower Poison worked (and how to counter it), or would plant/fungus-based poisons have confounded him?