Shares of Castlight Health Inc. /zigman2/quotes/201298689/composite CSLT +3.77% plummeted 24% to pace all premarket decliners Tuesday, after the healthcare information technology company announced a restructuring program that is in part a result to the unexpected loss of a large customer. The company said it plans to cut costs by 10% to 15% by the end of September, which charges expected to be recorded in the third quarter of 2018. Separately, the company reported a second-quarter net loss that widened to $14.0 million, or 10 cents a share, from $12.4 million, or 9 cents a share, in the same period a year ago. Excluding non-recurring items, the adjusted loss of 5 cents a share matched the FactSet consensus. Revenue rose to $37.8 million from $32.6 million, topping the FactSet consensus of $36.8 million, as 14.5% subscription revenue growth to $34.8 million beat expectations of $33.5 million. The stock had rallied 19% year to date through Monday, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.60% had gained 4.8%.