Articles about electrical troublleshooting
How to Identify and Repair Light Fixture Wiring Problems: The original fixture was wired using the sets of screws as terminals or a junction. Removing these wires and creating a color to color splice or matching the original terminal wiring configuration, then adding the wires from the new fixtures and installing a wire connector should work just fine.
How to Restore an Electric Circuit: Check the voltage of both legs of power to ground, or test receptacle outlets and devices in the home. If it is found that the voltage is still not correct you may need to call a qualified electrical contractor to make a few tests to identify the problem and make the necessary repairs.