Shares of Skyworks Solutions slid, after the Apple supplier said tougher competition for the iPhone maker's semiconductor business would cut into sales. Apple is the company's largest customer. Late Wednesday,

Skyworks’ stock saw its worst day in more than four decades, with analysts noting that Broadcom seems to have gotten in on the action for a lucrative iPhone socket.

Apple ( AAPL) supplier Skyworks Solutions ( SWKS) saw its stock drop nearly 25% Thursday as the semiconductor firm said that it's losing business with the iPhone maker to one of its competitors, which analysts believe to be Broadcom ( AVGO ).

The last couple of years have been challenging as the competitive landscape has intensified, says the company’s chief financial officer.