Measure the supply voltages and compare with the schematic. If they
are all too high, add in a dropping resistor.

Putting a series resistor would degrade the power supply regulation performance. This may or may not be important, depending on application.

The safest way to proceed would to put a (properly polarized) zener diode (or a series of several zener diodes, up to getting the required voltage and dissipation power) in series with the circuit, so that voltage drop gets (nearly) constant, independently of load variations.

73

Tony I0JX