You have two currently unrelated issues, the egg dropped on the floor and the pullets sleeping in the nests. Shall we try to keep them unrelated?
When a pullet first starts to lay it’s not unusual for things to be a little messed up. You might get soft shelled, really hard shelled, or no shell eggs. You can get yolk only, no yolk – just whites, double yolked, or some other type of weird egg. The same thing applies to behaviors. It’s not that unusual for a pullet to just drop her first few eggs wherever she happens to be, on the roost or walking around. Most pullet eggs, though small, are perfectly formed. Most pullets have control whenever they lay their first egg and lay it in place they want to make a nest. As complicated as the entire process the surprise is that so many get it all right.
But wherever they lay that first controlled egg is usually where they want to return to lay all other eggs after that. That’s why I want my nests open when my pullets are just starting to lay. I don’t want to teach them to lay somewhere other than my nests.
Why are your pullets sleeping in the nests? Are they only sleeping in the top nests? Chickens typically like to sleep as high as they can. The ones at the top of the pecking order get to sleep wherever they want and can be fairly brutal in enforcing those pecking order rights. You mentioned you have 18 pullets, though see my comments on Silkies below. How long is that roost? From the photo it does not look like that roost is higher than your top nests. It doesn’t look that long either, probably 8’.
What I think is happening is that your roost isn’t all that high and doesn’t have enough room. The ones lower in the pecking order that don’t fit are going to the highest place they can find, your upper nests.
So what can you do? My first suggestion is to raise that roost and install a second one. Put the first at least 12” away from the wall and the second at least 12” further out horizontally. I personally like them all the same height but some people stagger the height and it works out. Make sure they are higher than the nests.
To get them to lay in the nests I suggest you put a fake egg in the nests. I use golf balls but a lot of people like wooden or ceramic eggs. Some people use plastic Easter eggs, though those can be really light and are easily scratched out. Most chickens tend to like to lay where another chicken is laying. That doesn’t always work, but it can help a lot. Also try to keep the randomly dropped eggs cleaned up so they don’t think that is a safe place to lay.
In your case, especially if they are currently sleeping in the top nests, I’d block them off and try to get them to lay in the lower ones as soon as you get the roosts repositioned. With 18 pullets, four nests would probably be enough but there is nothing wrong with what you have. Since they are in the habit of sleeping in those nests you need to break that habit and give them a reason to look for other high place to sleep.
One problem you have is that Silkies cannot fly. Some Silkies like to roost, others are quite happy to sleep on the floor. Since they can’t fly is could be hard for them to get to the roosts, especially if you raise them. It’s possible those are the ones causing you a problem and they are sleeping in the lower nests because that’s all they can get to. That would mean what I wrote above may not be that important. What to do about Silkies?
One thing you could try is to build ramps so they can get to the higher roosts. They might use them, they might not. Another possibility is to build another low roost they can get to, maybe with a small ramp. Maybe make it a little higher than your lower nests if that’s where they are now sleeping. If they keep sleeping in the nests, make it very dark in the coop at night and move them to the new lower roost. They might eventually get the message that this is a good place to sleep. If the problem with pullets sleeping in the nests is only the Silkies in the lower nests, then put in a lower roost with a ramp and block off the lower nests while the upper nest are open.
I certainly cannot guarantee that any of this will work, you just can’t guarantee behaviors with living animals. But hopefully this will provide some help. Good luck!
We got our first egg today and it wasn't even in the boxes but in the corner of the coop. How should we arrange the nest boxes and roosts to encourage the ladies out of the boxes at night and in there to lay? Here are pics of how it is now but it can all be easily moved. 
