Clearly the current requirements are all over, but loosely it’s maybe about 20–30 mA on each rail per module, though a lot more on the +12 V rail for the VCO (I presume that’s due to the Nano). 16 modules at 30 mA each is about 500 mA, add some more to that on the +12 V side for each VCO. Depending on your choice of modules of course.
The RT-65B is rated, what, about 2.6 A on the +12 V side? But only 500 mA on the -12 V. So depending on exactly which modules you have, it’ll be marginal at best for -12 V.
It’s possible to set up two RS-25-12 to give you 2.1 A on each rail. If you also need +5 V you can get another Meanwell supply for that, or just add a 5 V regulator powered by the +12 V supply. Definitely more complicated than just hooking up an RT-65B, though.