I have an existing 3 way light circuit in my garage with 3 switches and 3 light fixtures. I am wanting to add two additional light fixtures and would like to run the two new fixtures off the middle of the existing 3 lights because of easy access. I wired the two additional fixtures and something is incorrect as the two new fixtures work but they are on all the time. None of the switches turn the two new fixtures off. I don't totally understand how the 3 way works but thought this would be easy. I run a 12/3 wire in series off the middle of the existing 3 fixtures. Do I need to use the 3 wire to the two new fixtures or do I only need 2? Thanks very much.