Harry Potter and the Flowerpot Conspiracy

When Harry awakens to Fleur having a bit of a "destructive home renovation" meltdown, he just thinks it's that time of the month again...until it's not. What on earth could it be? Why was Hermione shaking and looking like she was about to have a meltdown herself? Why was Gabrielle Delacour-Weasley about to explode? What conspiracy is the Weasley clan cooking up behind his back?