I recently added 3 more 20 amp fluorescent lighting circuits to an old hardware store. I installed all 6 lamp T8 High Bay Light fixtures...Problem came into play when I energized the new lighting circuits! When I switch any of the 3 new circuits on it causes all the other pre-existing 6 lamp fixtures that the store had to strobe like disco lights or cop car lights! Yikes! I have checked grounding...each fixture is bonded to frame with the line ground (I am using 12/3 MC Cable)... Is it a low voltage issue? Grounding? Shared Neutral issue? What are some things for me to consider and troubleshoot?