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

Griffin Land & Nurseries‘ (NASDAQ:GRIF) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Griffin Land and Nurseries operates a landscape nursery and real estate business. The stock price has fallen 12% over the past month, worse than the 3% decrease the Nasdaq has seen over the same period of time. The stock currently has a trailing PE Ratio of 46.60. For a full analysis of GRIF stock, visit Portfolio Grader.

Diamond Foods (NASDAQ:DMND) earns a F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Diamond Foods processes, markets, and distributes nut and snack products. The stock gets F’s in Earnings Growth, Earnings Momentum, and Earnings Revisions. Equity, Cash Flow, and Margin Growth also get F’s. The stock price has fallen 28.8% over the past month. As of Nov. 21, 2012, 34.9% of outstanding Diamond Foods shares were held short. For more information, get Portfolio Grader’s complete analysis of DMND stock.

This is a rough week for Omega Protein Corp. (NYSE:OME). The company’s rating falls to F from the previous week’s D. Omega Protein produces protein-rich fish meal, fish oil, and solubles. The stock receives F’s in Earnings Growth, Earnings Momentum, Earnings Surprise, and Margin Growth. The stock has a trailing PE Ratio of 25.20. For a full analysis of OME stock, visit Portfolio Grader.

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.