A few things for consideration:
(1) Are you 100% confident the noise is being emitted by the drivers (a), or is it perhaps the subwoofer enclosures/plate amps physically vibrating (b).
(a) - if yes go-to (2)
(b) - if yes go to ifi DC-blocker - cheap enough to try and see if it helps.
(2) Are you using a mix of balanced/XLR and unbalanced/RCA cables (a), or are they all the same (b)?
(a) If XLRs are an option, use these throughout, they are usually more immune to system noise, if not, use RCAs throughout.
(b) Are any of them so-called pseudo-balanced (screen connected only at one end), or some kind of weird design (box in the middle, Van den Hul carbon-fibre crap, unscreend DNM Reson, etc), if they are, ditch them in favour of something normal!
(3) Lots of valve amps have a ground-lift switch, check and see if the Viva’s have such, try changing the setting (safest to power-down - switch - then power-up again).
(4) Is everything plugged into the same outlet? More than one plug-board can be a bad idea, especially if you’re using the cheap shit that twats on forums insist is all you need. Even different wall sockets can be on different ring-mains, or stupidly-long spurs. It’s better to plug the whole lot into one high-quality plug-board and use long runs of power cable to reach the speakers.
(5) Any wanky mains cables in-use? There’s a cyclical fetish for using US-stuff, or even omitting an Earth connection. Don’t.
(6) Old house? Is all of the wiring to modern standards? Are the outlets you’re using definitely Earthed? Is the Earth of good quality (i.e.more than a strap to a central heating pipe). You can do a basic check yourself with a socket tester that incorporates an Earth impedance checker - something like a Kew Loopcheck107 - you could get a UK model and use it with a good quality converter plug.
(7) Easy common ground - grab an ESD plug -
And a cheap reel of 0.5mm Earth wire, undo a screw on the case of every bit of kit, including the (I assume) plate amps on the speakers, strip 1cm from the end of each wire and twist round the screw, then screw tight enough to hold, same at the other ends, twist 'em onto the binding posts on the plug, again if you got the UK version then you’ll obvs need a decent converter, but presumably all these things have Euro equivalents.
This way you have a common low impedance system ground which has a high impedance to Earth, so no risk of faults taking the wrong path and not tripping protection devices.
OK, I’m out of brane for now. Good luck!