Pest/Pathogen ID--Cyr. chailluana rust on leaves

[DBoro9]

Hi I have a Cry. chailluana that was kept with a cattleya that exhibited brown-rusty leaf damage. The infection/infestation seems to stunt leaf growth, eventually causing the leaves to dry and fall off. I separated the catt. and treated it with Physan which seemed to resolve the issue.

However, my Cry. chailluana is now exhibiting the same symptoms. I've been treating it with Physan but it is not improving. Can someone assist me w/ 1) identifying the pest/pathogen and 2) providing treatment recommendations. See photos.

I appreciate any insights.