After helping several ponies earn their cutie marks they eventually decided to retire, and let the cake twins and Cream Puff take over the business.
Where are they now?
Applebloom: After becoming old enough she helped her brother and sister in the harder chores like bucking down apple trees and pulling the plows. She is committed to the Apple family and loves them all, as her cutiemark signifies. She finally managed to earn her own hat like applejack did.
Sweetiebelle: Sweetie explored her love of singing and auditioned for musicals in Mahehatten. She got several parts, and eventually moved on to independent work. She eventually became a poster music she decided to go on a world tour and became a sensation all around Equestria. Her best hit song is "We are the Cutiemark Crusaders"
Scootaloo: Now, finding out what her cutiemark meant, was a bit tricky at first. She thought that the bolt meant she would be a 'lightning fast flier' but alas that never came to be. She realized she didn't have the magic that most Pegasi have to fly and remains flightless. But that didn't stop her, she became a daredevil under the name 'Flightless Eagle' and did several dangerous stunts in front of crowds with speed and agility. One of her biggest fans is Rainbow Dash.
Bases:
https://www.deviantart.com/stargazeandsundance
https://www.deviantart.com/velveagicsentryyt