Not sure about the whole "They only grow in the dark" but plants do need downtime. Even if a few hours. If your curious as to why, that Danny Danko over at HighTimes does a pod cast and the last episode I listened to one of them from this month, forgot the exact one, the cultivation segment went through this topic in some depth. Long story short, give them a few hours of dark. While 24/0 may work, they explain why its not the "ideal" method and why even a short night cycle will help your plants grow bigger.
I run DWC for both photos and autos. I give the autos 4 hours of rest each night. If I get anything less than 6oz from a plant I'm shocked, then again mine are monsters in that DWC, if I got only 2oz like someone posted above I'd ditch the strain or figure out where I was going wrong.