I have a similar issue.
I purchase WD and the 2-5 ep pack on one of my iPad's. I've then gone to the store, using the same account I made my purchase on, and installed it on my other iPad. I enter the game and it asks if I wish to buy the other episodes.
No, I don't want to buy them a second time. Does that also mean if I put it on my iPhone I'd have to buy it a third time?
I'm not willing to hit the buy again button just to see if the dialog says "You've already purchased this" without clarification - or the chance to get a refund if it takes my money twice.