Sobralia Andreae with black leaves

[chiquib313]

I recently acquired a Colombian Sobralia Andreae at the Redlands Orchids Festival and it has developed large black blotches on the leaves that eventually turn all black and fall off. What is the best treatment method to contain this and could this infect the other orchids in my collection? I was informed I should use a "systemic fungicide" but not sure which one would be most appropriate for this this plant. I have cut off all black leaves for now and sprayed with Physan 20 and separated the plant from the rest of the orchids just to make sure it does not spread. Attached are some photos. Anyone have any suggestions?