Brown patches under leaves: Phal. amabilis sick?

[Dragonar]

Hello guys,

I've purchased this Phal amabilis 3 weeks back. It started with 5 leaves new roots were growing but with 3 weeks, 3 of the oldest leaves had fallen off, the older roots had shriveled, and the new roots seems to be going dormant. I've attached pictures that seems quite off with brown patches under the leaves as compared to my other phals.

Do note that it is grown on a mount and I've added sphagnum moss to retain more moisture as it was grown outdoors previously here in Singapore.
I water all my orchids just by using a bowl and wetting the media with a spoon (nothing under the tap or hose for me) and this is done around evening due to my working schedule. For this phal, the moss would usually dry up by afternoon the next day (~20 hours), unless it was a rainy day where the weather is colder and it would stay wet for ~30 hours where I would then water it once again.

Not sure if the sphagnum did it more harm than good though. I'm suspecting some form of bacterial infection but it somehow seems to lead to signs of dehydration.