Talking to people who work for you about their performance is one of the most difficult tasks in the workplace. But, there are three quick changes to the way they talk about other people's behavior/performance that will dramatically improve the odds of a successful outcome.
First, put the description of behavior you're talking about ahead of the reason why you're having the conversation. That keeps those emotional protective shields from going up and blocking real communication.
This is hard to do, because most of our parents, early bosses, and role models did it just the opposite way. That means that you will, almost naturally, do the less effective thing unless you make a conscious effort.
I suggest that you rehearse your opening. That will help you put the behavior ahead of the reason for chatting. You'll probably have to practice the change, too.
Describe behavior the Joe Friday way. Just the facts. Drain off the adjectives. Then follow the description of behavior with a brief description of why that behavior matters.
The behavior you describe must be something visible or audible. It must be something that could be witnessed and can be described.
Do not, ever, use the words "attitude" or "always." Limit your discussion to observable behavior. Be specific about what happened and when.
Finally, once you've had your say, shut up. Wait for your subordinate to talk.
There are a couple of things that can happen next. Your subordinate might agree that you've got things right. Your subordinate might dispute your description of what happened.
Either way, you can now come to agreement on behavior. Then you're on your way to a meaningful discussion of how behavior should be different in the future. And what the consequences are for good and bad behavior.
This is simple and gets great results. So why don't more of us do it more of the time?
The answer to that one is easy. Old habits are hard to break and just about everyone we emulate did it the other way. If you do the preparation and practice to get these three things right, your conversations with subordinates about behavior will be much more productive.