Ruling Greninja's Water Shuriken Ability

[PsychedelicBreakfast]

"Once during your turn, you may discard a W energy card from your hand. If you do, put 3 damage counters on 1 of your opponent's Pokemon."

It says once per turn, but is that once per card? If I have 4 Greninja in play, could I discard 4 W energy for 120 damage?

 

[Brave Vesperia]

Yes, you may use it once per turn for each Greninja you have in play.