I would start by analyzing and breaking down the data into finer details. Is the decline in daily active users (DAU) occurring in a specific region, age demographic, or type of platform? I would examine the correlation between the drop-off and the timelines of product releases and marketing campaigns to identify any potential connections. Next, I would review user feedback collected from various sources such as interviews, surveys, app store comments, and social media. This will help me determine if users are encountering problems or if there have been shifts in their preferences or requirements. Additionally, I would explore potential technical issues. This would involve assessing performance problems, server malfunctions, recent updates to the product, or new bugs that may have emerged. Using insights from these sources, I would pinpoint and prioritize the issues to tackle them in a structured manner, aiming to effectively enhance the DAU.