Each agent is unique and has their own skillset. As a leader, your job is to determine these strengths and find areas of improvement actively. You can always sit down as say "This needs to improve." This is not the way I would handle the situation though. If I can take 30 minutes out of my day to watch and sit with my agent, see what they are doing and how they are doing it, I can provide true feedback into how to improve, instead of expecting them to do it on their own. If they have trouble multitasking there are also exercises that you can give your agents to help them cultivate this skill. I wouldn't want my agents to meet the average, I would want them to excel, and taking my time to pay attention to their needs is the best thing any leader or teacher can really do. Asking them outright, "What are you having difficulties with in your work-day?" also gives them the opportunity to tell you where they think they need help or improvement. Sometimes people learn differently than others, and you need to acknowledge this when you are working with a group that is under your care. Their performance is your performance. This is the same way I would treat an agent who is excelling, spend some time to see what they are doing right and share it with the team.