If you use the Yoast seo plug in on your site you may have heard about an error in their plug in that they have recently fixed. The issue they found was within the set up how of how images and attachments were treated.
Many users state that they have seen negative effects in their rankings and traffic over the time however there is no direct correlation and before assuming that this is the issue we recommend that you look further in to traffic and site changes before incorrectly assuming that this plugin is your issue.
Whilst it’s always good to find an issue so you can propose a solution don’t jump to conclusions otherwise you could be looking in the wrong place. Whilst Yoast accept there may have been some effect to some sites following their update there are a number of other factors that could come in to play.
If you aren’t using tools to track rankings then you should however we would recommend reviewing against Google algorithm updates and your own changes to the site.