Spots on Leaves Reason for Concern

[Junebug]

Both mounted divisions of my smbna 'Firefly' have recently begun exhibiting spots and discolorations on their leaves.

One plant has sunken dry white patches and browning tips on some of the newer leaves.

The other plant has no white patches...only brown circular spots and tips with lack of pigmentation along their borders. One of it's newer leaves exhibits an irregular brown pattern and yellow die back from the tip. There is one older leaf that appears to be yellowing as a result of old growth dieback.

After carefully examining the upper and lower leaf surfaces of both plants I cannot find any signs of insects other than ants and what appears to be ant poop. Wasps sometimes pay a visit. Tree frogs and lizards are in abundance.

These plants are suspended growing vertically with a Schomburkia growing between them. The Schom looks fine. They've been flourishing and have numerous swollen sheaths. The uppermost plant had a large decorative (unknown metal) and glass bead butterfly attached to the mount. Last week I suspected the rusting metal may have been causing the symptoms so I removed it from the mount.

I'm beginning to get concerned. I have Physan, systemic fungicides and listerine on hand but haven't begun any treatments thus far. The brown circular patches and white sunken patches began developing about 3 weeks ago. The latest symptom is the single yellowing leaf with irregular brown markings. It's decline happened rather suddenly.

Any thoughts or suggestions would be greatly appreciated.