Welcome to NGA ...
I am not going to address how to save your cuttings in this post because I think it may be more useful to you to learn how you initially set up your cuttings for failure ... please don't take that wrong.
You wrote:
I planted the cuttings in a pot a month ago or so, using universal soil and placing pebbles on the bottom of the vase for drainage.
This technique creates a perched water table. I can just hear you saying "WHAT ....."
I found a link for you that explains drainage in containers and perched water tables much better than I can.
https://deepgreenpermaculture....
Basically, the rocks at the bottom of your container inhibits drainage rather than enhancing drainage.
