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

Oil States International, Inc.’s (OIS) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). Oil States International provides specialty products and services to oil and gas drilling and production companies. For more information, get Portfolio Grader’s complete analysis of OIS stock.

Matrix Service Company (MTRX) earns an F this week, moving down from last week’s grade of D. Matrix Service provides specialized on-site maintenance and construction services for petroleum refining and storage facilities, as well as water storage facilities for the private industry sector. The stock gets F’s in Earnings Momentum, Earnings Revisions and Earnings Surprise. To get an in-depth look at MTRX, get Portfolio Grader’s complete analysis of MTRX stock.

This week, Helix Energy Solutions Group, Inc. (HLX) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Helix Energy Solutions is a marine contractor and operator of offshore oil and gas properties and production facilities. The stock also gets an F in Earnings Momentum. For more information, get Portfolio Grader’s complete analysis of HLX 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.