Similarly to identifying the strengths, your team's weaknesses need more analysis than mere observation. Is your employee who's perpetually late just lazy or do they live too far away? Is your team manager who constantly comes to you for approval being respected by their team (or you)? Or does the employee who always misses deadlines spend too much time helping their colleagues?

What do your employees which they had more support in? Where do they think they're lacking? Asking your team members to identify their own weaknesses might surprise you. Here, you need to be open-minded and leave your preconceptions at the door. Hear them out and let them tell you what they need to work on.