In general I would prefer independent power supplies for each channel resp. for each module. So you can better handling the GND management.
For your application this means an outdoor power supply.
Additional I would use for each module an own screened (e. g. aluminium) enclosure to avoid inteferences between the mudules in the kind of this one: 1590B | 1590 Aluminium Enclosure, IP54, 111.5 x 59.5 x 27mm | Hammond