Copper based fungicides seem to be a no-no for many ornamental
plants (most?). I tried a similar thing with asclepiads (Hoya
spp and Dischidia spp) with the same results - they turned a
peculiar shade of grey, then brown and finally black! It took
several plants a long time to recover and some never did. Good
ventilation seems to be the only way to prevent fungal attacks
without having to use noxious chemicals - this can be
problematical if you are trying to maintain a high humidity.
Cheers for now
Rogan Roth.