I just got back from a talk on coops and first aid by a local expert. She advises that the roosts be low, no higher than your waist. She said the area to fly down should be twice as long as it is tall. The birds have got to have clearance and area to get up and down...otherwise, they'll be trying to fly up/down and hit the wall (get injured) land hard (get bumblefoot).
From what I see, you have put an obstacle in their way to fly up/down by adding that second roost, and it doesn't sound like they have the room to fly down, even if you took the second roost down. Stair-stepping the roosts is your solution. That gives them a way up and down, and additional roost space (the alphas will take the top-most roost, the lower on the totem pole will roost below them). If they are staggered, they won't poop on each other, either!