Disease identification - brown spots on Renanstylis

[Jlin]

Hi everyone!
Haven’t posted in a while, but today I need your help to identify this weird spotting that appeared on my newly purchased Renanstylis Arizona Star (Ren. bella x Rhy. gigantea 'Panda #3').

I received the plant this spring from Asia, and it looked great when it arrived, no spotting! A few weeks later it started showing spots on some of the leaves and along the stem, and now the new leaves that are growing are covered in those spots already. (See pictures). It arrived bare root, and I planted it in a plastic pot with holes in loose sphagnum moss.

It’s the only plant in my collection that displays these symptoms and the first time that this happens.
I grow under leds indoors, temps above 20C at night, up to 30C when it’s really hot. Fans circulating the air every hour during the day, a couple of times at night.
I’m in Canada so not all products to treat this will be available but I have some Bactol, sulphur dust fungicide, and Phyton 27.

Any help is appreciated! This is not a common hybrid and I’ll like to try to save it🙏