Wasn't there a rule about magic items (which included potions)? Something about only being able to "hold" a number of them.
Edit: Yeah, chapter 22, can only use a max of 5 for the whole tourney & he just used 2 this round. & looks like he had used a flash bomb & nothing else. Tho, kinda weird he's the only one shown to have used any items at all (even in his battles).
Ps. Wonder if it used the Demon card he was supposed to get as a prize for the top 4.