
I have a willow-leaf ficus bonsai that has what appears to be a fungus. I have included a link to some photos here:
https://www.dropbox.com/sh/3xew3mnwh3f3ipd/7Jr3ulEMic
As you can see there are black spots, and lots of yellowing leaves (not so many in the photo since I remove the dead ones every day).
I had started using a general purpose fungicide / insecticide 3 weeks ago, once a week, but it's not improved, only seems to be getting worse. Is there an alternative solution to treat this? I've had this bonsai for over a year now and it's been fine until about a month ago. I really don't want to lose it

Thanks very much in advance for any assistance!!