This week, 6 Life Sciences Tools & Services stocks are worse, according to the Portfolio Graderdatabase. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, Illumina, Inc.’s (ILMN) rating worsens to a D from the company’s C rating a week ago. Illumina, Inc. develops, manufactures and markets integrated systems for the large-scale analysis of genetic variation and biological function. For more information, get Portfolio Grader’s complete analysis of ILMN stock.

This is a rough week for PerkinElmer, Inc. (PKI). The company’s rating falls to D from the previous week’s C. PerkinElmer, Inc. provides technology, services and solutions to the diagnostics, research, environmental, industrial and laboratory services market. For more information, get Portfolio Grader’s complete analysis of PKI stock.

Slipping from a C to a D rating, Luminex Corp (LMNX) takes a hit this week. Luminex Corp develops, manufactures and markets biological testing technologies with applications throughout the clinical diagnostic and life science industries. The company also gets F’s in earnings growth and earnings surprise. For more information, get Portfolio Grader’s complete analysis of LMNX stock.

Compugen Ltd. (CGEN) declines this week from a C to a D. Compugen Ltd. focuses on the therapeutic proteins and monoclonal antibodies to address unmet needs in the fields of immunology and oncology. The company also gets F’s in sales growth and return on equity. For more information, get Portfolio Grader’s complete analysis of CGEN stock.

ChromaDex Corporation (CDXC) is having a tough week. The company’s rating falls from a C to a D. For more information, get Portfolio Grader’s complete analysis of CDXC stock.

Genetic Technologies Limited Sponsored ADR (GENE) gets weaker ratings this week as last week’s C drops to a D. Genetic Technologies Limited Sponsored ADR is a biotechnology company that practices advanced DNA genetic research and testing. The company also gets F’s in sales growth, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of GENE 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.