Whose fault is it that your employee have lost their enthusiam? Initially, this person showed up early and left late because they were passionate about the contribution they were making to your organization. It seemed they cared just as much about your company as you do. Now, not so much. Something is missing, and it’s your fault. Your employees passion is like air in a baloon. You should be aware of how much air/enthusiasm they are working with, and do your best to raise that level.
The best way to do this is to start by hiring difference makers. People who have built in passion for your industry and the responsibilities they were given. From there, lead by example and show your own passion everyday. I know it’s a job, but it doesn’t have to be work. Don’t let the air out of the baloon.