Greenlight Capital, the hedge fund of billionaire David Einhorn, has been struggling in recent months, and investors had hoped for an upswing heading into the new year. Unfortunately, February did not deliver the much-needed good news, according to a report by CNBC.

In fact, both Greenlight Capital and Greenlight Capital Offshore fell by 6.2% over the course of that month. This brings the fund's decline in 2018 to more than 12%, year-to-date.

Monthly Update Reported Losses

Einhorn shared the news with his investor base in a monthly update on the fund's performance. This revelation comes after Greenlight Capital fell by 6.6% in January, while the Greenlight Capital Offshore portfolio suffered losses of 6% over that same period.

It's not immediately clear what the cause of the loss over the past month was. Perhaps investors and analysts can find clues in Greenlight's 13F filings for Q4 in 2017, released to the public in mid-February. Keep in mind, though, that this information is probably out of date by now.

According to the 13F report, Einhorn established 19 new positions in the fourth quarter of 2017, including a significant stake in "moderately distressed" retail giant J.C. Penney (JCP). Greenlight bought up about 6.4 million shares of the company in the final three months of 2017. (See more: David Einhorn's Greenlight Bought 6M JC Penney Shares: 13F.)

He also picked up new positions in CONSOL Coal Resources (CCR), Twitter (TWTR), Ensco PLC (ESV), and Time Warner Inc. (TWX).

Rough Year

It has been a difficult several months for Einhorn. His highly publicized investment in General Motors (GM), undertaken through the early part of 2017, crashed and burned. Analysts predicted that Einhorn was looking to make an activist move with the auto manufacturing company, attempting to convince investors to split up ownership of the company into multiple classes of stock. However, Einhorn was unable to sway a plurality of investors.

Compared to the S&P 500 Index – long used as a barometer for hedge fund performance – Einhorn's Greenlight Capital has significantly underperformed. Part of that is due to the fact that the S&P had its best January in about 20 years, gaining 5.6% in that month alone. It lost 3.8% over the course of February, though, bringing the year-to-date performance for the stock index to 1.8%.

Nonetheless, Einhorn's performance, both individually for the months of January and February, and across the year to date, has lagged the stock market. Hedge funds like Greenlight have increasingly struggled to match the S&P 500 benchmark in recent years, as investors in the hedge fund industry have grown weary of burdensome fees and lackluster performance, taking their money elsewhere.