If I have multiple Eevee with "Resonant Evolution" in play, can each of them trigger if I evolve one other Eevee? Or do I have to evolve a separate Eevee for each one?
If you have multiple Eevee in play, playing a card from your hand to evolve 1 of them would trigger every Resonant Evolution.
Source: Astral Radiance FAQ; TPCi Rules Team (2022-05-26)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH10_119
SWSH10_119