Weird. Mine get too much flow and tend to stay tucked, not enough flow and they will and tuck even tighter, moderate flow and they extend and sway. However, mine used to really stretch but for the past couple of weeks they've stayed kind of short. Moved them to the 125 two days ago and they stayed tucked. 10 minutes ago I moved them into a little lower flow but still more than they got in the 75 and they're opening up.I think you're right. The growers are almost in line with a power head. The lingerers are more sheltered and dark.