Weaknesses then fade from the picture. This avoids a fault-finding environment. Coaching is an endless task. Not completed after one month or year. Later, send the person to take courses.
Bad habits change only after much education.
People succeed or lose on the basis of their habits. A leader's job is to help people learn good habits to function well and bring about a successful life. The need to do something about incompetence. When a person starts to lapse from a previously held standard, firmness as well as fairness is needed. Confronting incompetence requires skill and timing.