Is treatment possible or should I toss this plant?

[NewBloom]

I sprayed all my orchids with Vermiliquid (a form of worm tea) because I found scale and suspected other insects were present.

I've post edabout this NoID den phal before but I need help. This plant has been exhibiting leaf problems since last year and it's slowly lost leaves. I've quarentined it from the collection.

In the photos you can see how the symptoms evolved from 2-4 days after I sprayed Vermiliquid. I removed that leaf Wednesday and another one seems to be following the same path.

I don't know what's the cause. A friend who grows orchids took a look at the plant and couldn't determine the problem either. There are 2 new canes growing that are currently unaffected.

I have not tried a systemic treatment yet. Should I go that route--and which product to use? Or does it seem to be too late/ dangerous to keep this plant around?

Thank you for your suggestions.