I would start by making your expectations (both results and behaviors) clear to the whole team, and also work out the best way to make the results of the team visible to everyone. After this, you can then talk 1-1 to each of the team members on their own areas and what they think is needed to achieve the results. It then gives you a way to coach the right behaviors in a way that would help them achieve better results and faster. With team performance, it always starts with clear expectations, visible expectations, and coaching around the behaviors that will deliver the expected results.