Hmmm, sounds like a voltage problem. The LEDs at night can suck up a lot of amps. Maybe try to bump up your amps if it is a 12volt (at least 1 to 1.5) or check your power cable.
Inexpensive way, connect "T type BNC" to single channel you want to view. One cable in one cable out. Connection should be Ok as long as it is not too far away from quad.