Sudden death of Aerangis

[Lars Kurth]

I was wondering if it could be black rot(bacterial erwinia/pseudomonas) or brown rot(fungal pythium) both of which move pretty quickly

Yes, I did cut the plant and there was no ring. I cut through the central rosette to see what the tissue was like and it was totally mushy, a brownish/blackish colour, all along. Probably Pythium or Phytophthora. Definitely not Fusarium.