Iris - Marks down the racers whose place will be the same or better than their odds suggest
Snapdragon - Predicts correctly in even-numbered races
Nazuna - Predicts randomly
RESULTS: x50, x20, x100, x10, x30
Interestingly enough, x20 made it to the 2nd place and was not marked by Iris. This would mean she marks only those who'll do better than their odds.
So far it seems Snapdragon's and Streptocarpus's gimmick is that they correctly mark the top 3 in a random order in their respective races.