I'm not sure of your set-up. With that few hens your coop may be pretty small. If you can, I'd make sure I had two nests. In normal circumstances, you would only need one nest for four hens, but this situation is not quite normal. They will soon fully integrate with your two older hens when they finish maturing, but more mature chickens can be pretty bad bullies toward younger ones. They will probably eventually all use the same nest but a second one might come in handy for the transition. But if you cannot give them a second nest, don't obsess about it. They will work it out but there might be a transition period.
Put a fake egg, such as a golf ball, ceramic egg, wooden egg, something like that, in each nest to show them where to lay.
When I raise new pullets with the flock, some often use different nests than the older hens when they first start to lay. Some start off using the same nests as the older hens. I find very little consistent with chickens. Most may normally do one thing, but I always have some that will do something different.