Every tank is going to be different, but you may need to dim the light a bit further. Remember that dimming LEDs is not a linear function--dimming to 50% (which is really dropping the power by 50%) gives you light intensity greater than 50% (more in the range of 57-60%) because LEDs become more efficient as you drop the power. So JParisi's dimming to 40% is probably dropping the light level to 50% of full power, which isn't a bad place to start...from there you'd want to tweak CO2 input and supplementation until everyone looks happy. Once that's done, if you want to have faster growth then start slowly bumping up all your levels. It's all a balancing act.
Hope this helps!