Sorry, Don, if you did not add any water .
I am wondering how humidity is that high because you said earlier that " most of the humidity seemed to be rising "
It can only happen when soil is too wet, or temp is too high
When humidity is high, you will see drops of water (from condensation) running down the zip bag sides .
To remove those excessive water, take a newspaper and fold it into layers
Insert that paper inside the bag as shown in the picture below.

(never mind what is in the
bag, I just take something to show how to insert the newspaper in the
bag)
The newspaper will absorb quickly all the water and become wet. Get rid of it and insert another one . The second sheets of paper might get wet too but less than the previous one . That is fine
That way the stem wont be mushy
Mold only happen when the cutting or part of it is dead