That must be the beginner version: with only one colour of marbles.
I think the game would be pretty darned hard with only one color of marbles! It'd be impossible to complete any potions!
I didn't count the marbles in mine, but I was thinking of adding the spare marbles in (I think it's two per color) just to help prevent a single lane from running empty.
Maybe the best solution is simply to play the game with only 2 or 3 players. Less downtime, less likely to have a lane go empty or nearly empty.