Watersanswered grow question 6 years ago It is possible that that 5th plant is actually a photoperiod plant that got mixed up with your auto seeds, or it could just be a late blooming auto. Switching to 12/12 will give you an answer and no cutting the number of hours of darkness will not upset your others. However, the probably they grow as big as they would have under the 20/4. Try putting the 4th plant in total darkness(outside your tent) for 48hrs and see if that flips it. That way, your others can keep powering on.