Is There a Phalaenopsis Dr. In The House?

[Djarum Black]

Hi Gwen,

Mesophyll collapse in many cases is caused by excessive cold. That’s why I asked if you had watered with really cold water or something like that.
It could also happen if you left it outside and the temperature dropped way to low.
If it is spreading, it means that it is probably infected with some type of bacteria. Like an open wound. I would sterilize a razor and cut the leaf off till there is no black left. The put something on the new cut you made, like cinnamon if you have some.
It might not be very pretty for a long time, but I think it will live.