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

Koppers Holdings (NYSE:KOP) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Koppers Holdings manufactures carbon compounds and wood treatments. Shares of the company have fallen 10.3% from a month ago. This is worse than the S&P 500’s 6.9% decline for the same period. To get an in-depth look at KOP, get Portfolio Grader’s complete analysis of KOP stock.

China Green Agriculture (NYSE:CGA) is having a tough week. The company’s rating falls from a C to a D rating. China Green Agriculture engages in the research, development, production, and sale of various types of fertilizers and agricultural products in the People’s Republic of China. The stock price has declined 7.9% from a month prior. For more information, get Portfolio Grader’s complete analysis of CGA stock.

This week, Balchem (NASDAQ:BCPC) drops from a C to a D rating. Balchem develops, manufactures, and markets of specialty ingredients and products for the food, nutritional, feed, pharmaceutical, and medical sterilization industries. The company’s stock price has declined 8% from last month.  For a full analysis of BCPC 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.