Not sure but Nutaku on the new section say:

Monday, May 25th 2016
The second phase of the first Flower Knight Girl event has now begun. The event's duration has been extended to the 3rd of May, 2016, to compensate for the squad issues we have addressed. A discount has been added to the Premium Gacha Machine with the Nutaku Gold Payment option.
The Discount can only be used once per account.

Maybe is related, maybe no, I've no idea of what squad issues the game suffer on the past days XD.

PS: I can't see any discount on Gacha Premiun with gold o_O.