What is happening:
When starting the game as a unicorn, after completing "Believe It Or Not" and the quest involved with a Magic Talent Mark, and then going to Ponydale and starting "An Equestrian Werepony in the Evershade," if you then go into the Evershade, you will find both the group of foals and a green pony, who I think is called Arcane Gleam. If you do the quest with Arcane instead of the foals, you will then grow up, and the foals will be gone, skipping the rest of the werepony quest.
What should be happening:
You should not grow up until after doing both the werepony quest and the Arcane Gleam quest.
Steps to reproduce the issue:
Start as a unicorn, do "Believe It Or Not" and the Magic Talent Mark quest. Then head to Ponydale and speak to the foals at Town Hall. Head to Evershade, then skip talking to the foals and go straight for Arcane Gleam.