Software startups continue to be important drivers of economy globally. As the initial investment required to found a new software company becomes smaller and smaller resulting from technological advances such as cloud technology, increasing numbers of new software startups are born. Typically, the main argument for studying software startups is that they differ from mature software organizations in various ways, thus making the findings of many existing studies not directly applicable to them. How, exactly, software startups really differ from other types of software organizations as an on-going debate. In this paper, we seek to better understand how software startups differ from mature software organizations in terms of development practices. Past studies have primarily studied method use, and in comparison, we take on a more atomic approach by focusing on practices. Utilizing the Essence Theory of Software Engineering as a framework, we split these practices into categories for analysis while simultaneously evaluating the suitability of the theory for the context of software startups. Based on the results, we propose changes to the Essence Theory of Software Engineering for it to better fit the startup context.