The ratings of 7 Chemicals stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Ashland Inc.’s (ASH) rating weakens this week, dropping to a D versus last week’s C. Ashland Inc. is a global specialty chemicals company and provider of products, services, and solutions for a variety of industries. The company also gets F’s in sales growth. For more information, get Portfolio Grader’s complete analysis of ASH stock.

Tredegar Corporation (TG) gets weaker ratings this week as last week’s C drops to a D. Tredegar Corporation manufactures plastic films, elastics and laminate materials, mainly for personal and household care products and packaging and surface protection applications. The company also gets F’s in operating margin growth, earnings growth, earnings revisions, and earnings momentum. For more information, get Portfolio Grader’s complete analysis of TG stock.

Slipping from a C to a D rating, OMNOVA Solutions Inc. (OMN) takes a hit this week. OMNOVA Solutions Inc. develops, manufactures, and markets emulsion polymers, specialty chemicals, and decorative and building products for industrial, commercial, and consumer markets. The company also gets F’s in sales growth, operating margin growth, and earnings revisions. For more information, get Portfolio Grader’s complete analysis of OMN stock.

BioAmber, Inc. (BIOA) experiences a ratings drop this week, going from last week’s C to a D. The company also gets F’s in sales growth, earnings surprise, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of BIOA stock.

ICL-Israel Chemicals Ltd. (ICL) earns a F this week, moving down from last week’s grade of D. For more information, get Portfolio Grader’s complete analysis of ICL stock.

This is a rough week for Senomyx, Inc. (SNMX). The company’s rating falls to D from the previous week’s C. Senomyx, Inc. discovers new proprietary flavor and fragrance molecules for use in a wide range of consumer products. The company also gets F’s in earnings surprise and return on equity. For more information, get Portfolio Grader’s complete analysis of SNMX stock.

Marrone Bio Innovations, Inc. (MBII) declines this week from a C to a D. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of MBII 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.