no card ever has an effeect that happens at the end of the turn. The abilities (including passive abilities) are used when the creature attacks (or when it is the permanent's 'turn'). If this creature has the ability of granting 4 or 5 extra max hp per attack...with adrenaline...that's up to 20hp per turn per nymph. Then if you have 6 of them, all twin universed... that's 6x20x2...that's 240 max hp gained per turn. Although this card doesn't seem particularly overpowered, if you factor in the game mechanics and other cards that can be used with this one, it becomes very overpowered.
