Mutual funds giant Fidelity Investments reportedly cuts its valuation for tech unicorns Dropbox and Cloudera, among others, in its latest valuations report for February, released Wednesday. These reports are closely watched by Silicon Valley investors to assess private startups which, unlike publicly traded companies, have no obligation to share detailed accounts of their financial performance.

Enterprise software maker Cloudera suffered the largest markdown with a 38 percent dive in valuation, compared with January. Other big markdowns include cloud storage firm DropBox, down 20 percent, and health-benefits broker Zenefits, down by a fourth and currently 65 percent below Fidelity's May 2015 purchase price.

The Boston-based financial services company had raised its valuation of Dropbox in December. Investors have grown increasingly vary of startups which rely on subscription sales because of their reliance on expensive marketing to corner market share, the Financial Times noted. Cloudera, which was expected to go public last year, has delayed listing at a time of volatility in the stock markets.

The reappraisals come amid growing scrutiny of the sky-high valuations of privately held Silicon Valley tech companies. Attention has focused squarely on the so-called unicorns, defined as companies estimated to be worth more than $1 billion.

On Wednesday, Fidelity's monthly filing showed it had increased its investment in Snapchat in February at similar valuations to the fund's investment in the company last March. The exact per-share price wasn't clear because Fidelity didn't disclose its latest total shareholdings in the company, according to the Wall Street Journal.