Yes. The proposed method of cutting wall-outlet 120V AC voltage to all 4 bricks is another alternative. These controllable power outlets usually have a relay inside but as pointed out, you don't have to mess with high-voltage wiring.
But again these controlled outlets are a Thing 1 discussion item...not a Thing 2 solution.
Anyway, along the lines of Thing 1 discussion, it may not be common knowledge that many of the DC-to-DC converter modules have a reverse-protection diode on the input. Here is a close-up of what I believe is the DC-to-DC module that Clem has:
What this means is you can apply 18V AC brick voltage to these modules. And for low power applications, then the half-wave rectification and modestly sized input capacitor (100 uF shown here) might just do the trick! It might even turn out that ~9V DC (average) was all this module could put out when driving multiple 12V DC relays! I was wondering where the diodes and/or bridge rectifiers for AC-to-DC conversion were in Clem's various photos and this is what I came up with. Again, this is Thing 1 "just talking..."