This week, the ratings of six software stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Workday, Inc. Class A (WDAY) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Workday provides software-as-a-service solutions for managing global businesses, combining a lower cost of ownership with an innovative approach to business applications. For Portfolio Grader’s specific subcategory of Equity, WDAY also gets an F. To get an in-depth look at WDAY, get Portfolio Grader’s complete analysis of WDAY stock.

This week, SRS Labs’ (SRSL) rating worsens to a D from the company’s C rating a week ago. SRS Labs develops and licenses audio and voice enhancement technologies. The stock gets F’s in Earnings Growth and Margin Growth. For more information, get Portfolio Grader’s complete analysis of SRSL stock.

Taomee Holdings Ltd. Sponsored ADR (TAOM) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Taomee Holdings produces children’s entertainment. The stock gets F’s in Earnings Growth, Earnings Momentum and Earnings Revisions. Margin Growth and Sales Growth also get F’s. The volume of trades has dropped off significantly in the past week, down to half the previous rate. To get an in-depth look at TAOM, get Portfolio Grader’s complete analysis of TAOM stock.

Mavenir Systems, Inc. (MVNR) is having a tough week. The company’s rating falls from a C to a D. The stock gets F’s in Earnings Revisions and Equity. For more information, get Portfolio Grader’s complete analysis of MVNR stock.

Zix Corporation (ZIXI) earns a D this week, falling from last week’s grade of C. Zix provides secure, Internet-based applications in a Software-as-a-Service (SaaS) model. The stock gets F’s in Earnings Growth, Earnings Momentum and Earnings Surprise. The stock has a trailing PE Ratio of 75.40. To get an in-depth look at ZIXI, get Portfolio Grader’s complete analysis of ZIXI stock.

This is a rough week for Digimarc Corporation (DMRC). The company’s rating falls to D from the previous week’s C. Digimarc provides media identification and management solutions to commercial entities and government customers in the United States and internationally. The stock receives F’s in Earnings Momentum, Earnings Revisions and Equity. Margin Growth and Sales Growth also get F’s. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. For more information, get Portfolio Grader’s complete analysis of DMRC stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.