Ah Yugioh. What can I say about this series, and it's sequels that has not already been said.
Okay, I got on. The next series will be DUELS IN SPAAAAAAAACCCCCCCEEEEEEEEEEE!!!!!!!!
Seriously though. Since it hasn't been put out there (and if it has, feel free to verbally mock me) I have two theories on the Aki/Akiza losing her psychic powers front.
1) They were based on powerful negative emotions (ie hate, which she had in excess, but as she became kinder and more at peace, they eventually became more manageable, before fading completely)
2) It has something to do with the current villains of the Arc. They Gave Team Catastrophe the card of darkness, so they clearly are also capable of making cards attack for real, but in a different manner from Aki. They brought her down to normal
to take out the competition.
I lay down these two theories and end my turn.