Declining Usage After Launch

Spotify is experimenting with a new collaborative playlist feature that allows multiple people to edit a single playlist in real time. This functionality is intended to boost social interaction and make music discovery more engaging by enabling friends to curate playlists together. After a limited rollout to 10% of users, early metrics indicate that daily active usage in this treatment group has dropped by 8% compared to the control group who do not have access to the feature.

How would you approach diagnosing the cause of this decline, and what steps would you recommend before deciding whether to proceed with a full launch?