Do a Google search for your state’s trappers association. They may have a list available of licensed trappers to help you. These are experienced individuals who probably have the equipment, scents, and bait to specifically target the predators lurking around your flock. That is my best advice. They may be able to identify tracks in the area (take photos of any odd tracks you see for now maybe?). Get yourself a game camera to put outside the pen or a nest cam to help identify the potential predators.