G'day Mike, sorry about getting your name wrong, just another senior moment, starting to happen a bit too often though.
I guess with the high humidity you have, fungus problems will happen more often than in a lower humid area.I just sprayed mine again with mancozeb, next week I'll try Kocide followed up with Rovral.
Mine are also in the patio area , so may not get enough air movement, though it is pretty ''fresh '' out there.At the moment as they are cuttings just sending out their first growths, I don't want to risk putting them in the shed, as there are cats galore that would destroy them all too easily.
Hopefully, someone will know the name of the correct fungicide to treat this ailment.