Google does several core ranking updates per year and confirms very few updates throughout the year. Specific to broad core updates, Google has said numerous times that you cannot do anything specific to fix your rankings. Google’s previous advice is, “there’s no ‘fix’ for pages that may perform less well other than to remain focused on building great content. Over time, it may be that your content may rise relative to other pages.” If your rankings did change recently, it may have been related to this broad core ranking update
and not necessarily related to a technical change you made on your website.