Ah yes, I see the 2 lower ones now and an upper perpendicular one.Oh NO! We have 3 48" roosts.
I agree with the other suggestions to add an even lower roost for the younger ones and carrying them there at night if necessary. I've had to do that before. But, you may run into another problem again with upper birds pooping on the ones below when they're stacked above each other like that.
Interesting idea to put dividers on the roosts. Do you have a picture of what that looks like please?Even if it seems like there's plenty of roost room, it doesn't mean they'll ever share. I would add yet another roost, lower than the others. And I actually put dividers on roosts to maintain peace....