The company that makes Candy Crush Saga is now public and trading on the New York Stock Exchange, and investor concerns are already weighing down the share price.

King debuted this morning with an initial public offering price of $22.50. It is now trading at around $19.90 to $20.70, which is down more than 11 percent. This puts the London-based company’s value at about $6 billion. Most of that worth comes from the match-three puzzle game Candy Crush Saga, which is free to download but makes millions of dollars every month from in-app purchases. King’s share price is dipping mostly due to fears that the developer is over-reliant on Candy Crush and that the mobile phenomenon’s growth is slowing. The company’s monthly active users has started to stagnate now that it has reached more than 400 million. That may force it to spend more on acquiring users who are worth less.

“The valuation is troubling considering that most of the revenues are derived from Candy Crush and King has experienced a decline in monthly unique players,” Jonathan Reich, chief operating officer of mobile personalization app Zedge, told GamesBeat. “This does not bode well for the future valuation and may point to sustainability issues.  It would be healthy to see growth across a broad portfolio of titles, which is one of the key risks in this IPO.”

Candy Crush Saga debuted in 2012, and it followed up a web-only version called simply Candy Crush. In 2013, King’s puzzler was the most-downloaded game on both Android and iOS. It now has more than 100 million players. In addition to that title, King has a number of other popular mobile games like Pet Rescue Saga and Papa Pear Saga. But while Candy Crush Saga has a triple-digit DAU, Pet Rescue Saga — its next biggest game — has 15 million.

The company says that it has more than 144 million daily active players across all of its games. It also hosts 1.4 billion play sessions each day.

Last year, King earned $568 million in profit on revenues of $1.88 billion.

King is the first major social-game publisher to go public since Zynga in 2011. The FarmVille company’s IPO valued it at $7 billion, but its share has since nose dived. The company is now worth around $4.2 billion as the company failed to re-create the success it found with its early Facebook games.

Zynga is trading down about 4 percent today to $4.64 per share.

Zynga is now trying to shift to mobile, which is a market sector that King is already well established in.

While King is best known for its mobile games now, it also has some of the top-performing titles on Facebook. It also has its own online gaming platform,, which also generates revenue.