Hi @Gaucho
Welcome to the Sonos Community!
I would mark @ratty’s reply as the Best Answer, but I’d always look for free - or cheaper - options first.
The fact that all 3 Amps are in the same location and are not ethernet-wired is a problem. End of story. They will be sources of interference for each other.
If you can, the best option would be to have all three wired individually to a network switch, with WiFi disabled on all-but-one of them (leave one on in case you want to expand with wireless speakers at a later date). The switch would be wired to the router (or main node of a mesh), not to a wireless mesh node. Alternatively, you could daisy-chain them with ethernet cables, with one cable leading back to the router.
A final option would be to leave them all on WiFi, but to separate them by 1m.
I hope this helps.