What is wrong with my ficus? Black tips on the branches

[rokelka]

Hello, I'm still a beginner trying to learn about growing trees. I recently bought this ficus. It looks like it was pruned before sale (some leaves were also cut in half or partly and ends of the leaves were turning black) and pruned branches had black tips. I thought that it's just sap that has dried, but all branches affected by this black stuff started dying back hard, tree dropped probably more than half of its leaves and is dropping more on touch, and some of them before dropping are changing colors just like in the first picture. There are also some buds that are turning completely black, but on every other branch they are growing fine.
Tree is potted in akadama that I'm keeping constantly moist just like my other ficuses, and none of them have this issue. Can anyone tell me what are these black spots/tips and what do I do to control this situation before whole tree dies? I've been cutting these black ends off, but maybe I'm just overreacting and it's indeed just a sap and branches dying back is caused by some another issue?
Pics -

https://imgur.com/a/nX8rjQu

 

[Forsoothe!]

That's a healthy new bud pictured, a sign of a ~healthy~ plant. I speculate that the soil may be staying too wet. Just because it's in bonsai soil doesn't mean things are peachy keen. You don't know how long it has been in there, or what the core is like. You don't really know about the moisture level at the core unless you have a tester which can be had for $10 to $20 at any garden store. I would want to know.

 

[sorce]

Welcome to Crazy!

Straight Akadama can be pretty wet for these.

Tis the season.

Sorce