I would generalize this as don't gossip or speak negatively about other team members. When you talk to your staff, assume that whatever they hear about another

I would generalize this as don't gossip or speak negatively about other team members. When you talk to your staff, assume that whatever they hear about another dev, they are thinking about themselves. If you say "so and so is slow", they will possibly worry you think that about them. There is room for getting feedback among members. Like "I noticed so and so had challenges shipping X on time, what do you think was the cause?" – this is subject-focused, impersonal and helps with growth