Mirae Asset Emerging Bluechip mutual fund is down performing?

Hey this fund was a topper in large cap category. But for last 1-1.5 yr it's doing very bad. What is your take on this? Were you familiar with this before? How do we know this won't happen to any other fund we pick? It's numbers look good but then after you get in and into an year it goes down. What would you do?