Use the diluted Hydrogen Peroxide suggested by
@0soyoung, spray the "woody" branches and trunk. I'd avoid the leaves as they are fairly delicate and it might de-foliate on it's own.
Mildew like you get in a damp basement with poor air flow. I don't think the tree "has it" in as much as it's surface mildew. Indicative of a moisture problem, in my opinion.
The area you have it sited is a poor option, to me. Too much dampness and most likely poor air movement with inadequate sun exposure.
Note the remarks regarding chlorosis, i.e. soil compaction and poor aeration. PH levels are the least of your concerns here, focus on siting and better timed watering. Ditch the meter.
Chimera? Greek mythology is cool and who doesn't like a good genetic mutation? But that's not what is happening here, waterlogged roots are the most likely culprit.
BRT's are pretty disease/fungal proof, might get 1-2 scale insects in a blue moon...I mean virtually bulletproof......but any containerized tree can suffer/die from waterlogged roots....
Again, trying to help. Up here, this tree would probably command $1500-$2500 from a bonsai nursery. I'm sure you paid a pretty penny...…..
…….but putting "security" before "health" is bad Spanglish in my book...……
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
....or Fraunch, Jerkman or my favorite, Trailermerican!!!!
![Er... what? o_O o_O](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f635.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
get that thing off the ground and proudly displayed or I'm gonna' wig-out!!!!
![Wink ;) ;)](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
![Big Grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)