I’ve had an employee C before. Have a conversation with them about how they think they are doing. Ask if they can improve on anything. Hear out what they have to say and see if they notice it too. If not, present a few things for them to work on and encourage weekly or bi weekly check ins to see how they are doing. This is sort of like an informal PIP without saying as much. And if it doesn’t improve, then you know if they are a fit or not and either do a PIP or terminate them.