You don’t know what the problem is; you know some facts which says something about the problem.
You are going to do something to motivate the employee and not de-motivate. If you end up de-motivating your employees, I doubt your intention or your qualification to give feedback.
Many approach a feedback session as if it was a session to ask the employee to leave. If you think you can get a better person please do so, but as long as you want to keep this employee it’s because you need him/her.
Feedback is about finding out the problem and then giving a solution and most of us think we already know what the problem is.
Feedback is also about negotiation and reaching a solution which is agreeable to both and which leads us to the goal in some way. The bottom-line being how fast is it realistic for us to reach the desired goal and if it is not do we have another option.
If you don’t think there could be any solution to the problem why go for a feedback session anyway.
Remember most of the problems that we encounter are personal problems affecting professional lives. So your job is to let the employee open up and tell you what is the problem that he/she is facing.