Just a few years ago , Under Armour was on fire.

Revenues for the sportswear giant were growing at an incredible clip. Profits were robust. Its celebrity endorsers included the basketball star Stephen Curry, the golfer Jordan Spieth and the ballet dancer Misty Copeland. Investors, enamored with the company and its high-tech apparel, sent its stock soaring to a high of more than $51 a share in the fall of 2015.

The hot streak is decidedly over.

The latest wave of bad news started on Sunday night when the company, which is based in Baltimore, confirmed it was assisting federal authorities who are investigating its accounting practices and related activities dating back to 2017.

Then, on Monday, Under Armour reported revenue declines for the fifth straight quarter in North America — its biggest market — and cut its forecast for the year, predicting that revenues for the entire company would grow only 2 percent this year. The company’s stock sank over 18 percent on Monday, ending the day just above $15 a share.

And Under Armour is already dealing with leadership changes. Last month, the company announced that Kevin Plank, who started Under Armour from his grandmother’s basement more than 20 years ago, was stepping away from his role as chief executive on Jan. 1.