May I suggest you a better criteria to determine the winner,from next competitions?
If 2 opponents have fe. 1 correct score guessed ,the 1st criteria should be in which line is the corect score,who has the score in 1st line(or in a line higher than his opponent) will win (as it's about guessing the score and not the goal difference) if both have guessed the score in the same line then other criteria may apply