This week, the overall grades of three life science stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Luminex Corporation’s (LMNX) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Luminex develops, manufactures and markets biological testing technologies with applications throughout the clinical diagnostic and life science industries. In Portfolio Grader’s specific subcategories of Earnings Revisions and Earnings Surprise, LMNX also gets F’s. The stock has a trailing PE Ratio of 121.80. To get an in-depth look at LMNX, get Portfolio Grader’s complete analysis of LMNX stock.

Bruker Corporation (BRKR) earns a D this week, moving down from last week’s grade of C. Bruker designs, manufactures, markets and serves proprietary life science and materials research systems based on its core technology platforms, including X-ray technologies, magnetic resonance technologies, mass spectrometry technologies, optical emission spectroscopy and infrared and Raman molecular spectroscopy technologies. The stock also gets an F in Earnings Growth. The stock currently has a trailing PE Ratio of 58.60. For a full analysis of BRKR stock, visit Portfolio Grader.

BG Medicin’s (BGMD) rating weakens this week, dropping to a D versus last week’s C. BG Medicine is a life sciences company focused on the discovery, development and commercialization of novel diagnostic tests based on biomarkers for high-value market opportunities in healthcare that it identifies. The stock gets F’s in Equity, Cash Flow and Sales Growth. For more information, get Portfolio Grader’s complete analysis of BGMD 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.