This week, 3 Life Sciences Tools & Services stocks are worse, according to the Portfolio Graderdatabase. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Harvard Bioscience, Inc. (HBIO) slips from a D to a F this week. Harvard Bioscience, Inc. develops, manufactures, and markets tools used in drug discovery research and pharmaceutical and biotechnology companies, universities, and government laboratories. The company also gets F’s in operating margin growth, earnings growth, and earnings surprise. For more information, get Portfolio Grader’s complete analysis of HBIO stock.

This week, pSivida Corp.’s (PSDV) rating worsens to a F from the company’s D rating a week ago. PSivida Corp. develops drug delivery products for treatment of back-of-the-eye diseases that are administered by implantation, injection, or insertion. The company also gets F’s in operating margin growth, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of PSDV stock.

Sequenom, Inc. (SQNM) gets weaker ratings this week as last week’s D drops to a F. Sequenom, Inc. is a molecular diagnostic testing and genetics analysis company. The company also gets F’s in sales growth, earnings revisions, and earnings momentum. For more information, get Portfolio Grader’s complete analysis of SQNM 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.