Did you discuss this at a 1:1 with the person?

As to introspection, perhaps some more is called for. You refer to your colleagues as "subordinates" and think of yourself as "boss, leader..."

That's not the proper mindset to be successful as a manager in high tech. You're there to clear hurdles for individual contributors who are more technical than you (if they're not, you are either a junior manager managing even more junior engineers, or your company does not have a technical track to attract/retain good engineers), so that they can do their jobs more efficiently.