Everybody has their own opinion as to what is best. Ladder roosts have been successfully used for thousands of years as well as having all the roosts on the same level. They both have their advantages and disadvantages.
Chickens tend to want to roost on the highest place they can get. The dominant ones get to choose where they sleep and the less-dominant have to make do. There is often some squabbling as they sort this out, usually every night. You’d think they’d learn and just go to where they belong relative to the pecking order, but nope, not my bird brains. Even with plenty of roost space the same height some spots on the roosts are preferred more than others. In mine the favored spot is near the window.
Some birds are more brutal in enforcing pecking order rights than others, especially if you are integrating immature birds with mature birds. I’ve seen a hen leave her normal spot on the roost to go harass younger birds at the far end of the main roost. These harassed immature birds usually leave the main roosts and look for a safer place to sleep. With your ladder roost that might be the next level down instead of your nests.
Yours are still pretty young, they have some growing to do, both size and maturity levels. You will probably see more changes. As long as they are not sleeping in your nests you are doing fine. If some start sleeping in the nests putting in another roost so you have more roost space higher than the nests is usually a real good thing to do.
