I noticed this yesterday. What do you guys make of it? I'd think it was mechanical or edema but, I had another phal succumb a couple months ago. Temperature has been stable, humidity in the 50% range, watering the moss as it approaches dryness. It could have been dripped on and that is very hard to 100% eliminate.
I've lost a lot of plants this summer and I'm pretty sore, so be gentle.