tri-rail power supply from cheap buck converters
The circuit will not work unless either


the -12V converter is an isolated DC-DC converter, or
it is intended to produce negative voltages and actually has a positive GND contrary to your labeling.


Cheap converter modules that don't specify otherwise are likely to be non-isolated. This means that the input negative/GND and the output negative/GND are internally connected, so your circuit will short out the -12V converter.