Dear Tired:
Your staff needs to understand that when they are at work, there is more to it than just doing nails. Consider assigning everyone a job or project that will help improve business. In my salon I have one tech that handles promotions to clubs and organizations, another handles all in-house promotions, and another handles bridal. Sometimes we all clean out cabinets and closets.
If they don’t want to stay, then the hours should be offered to other techs who will stay and try to build their clientele.