what causes the base of the phulb to becoming limp?

[kindrag23]

This is my 2nd Catasetum to have this issue. The plant acts okay and looks great then it starts to droop and the base of the new growth becomes wilted limp acting. Then the leaves begin to drop off, what causes this. My black pearl i am afraid is not going to survive because its back phulbs are small..i dont want to lose it.

It came in bark mix and i left it in fresh bark mix. The roots are healthy and the plant did fine until about 4 days ago. Now its all wilted...

I water when dry it gets the same light as my others, no major changes. But the humidity has been 50% or higher last 2 weeks....nothing has changed whatbhas caused this?