It's really hard to say, further observation might give a clue....or not.
I'd keep up with the high protein treats to augment the layer feed(16%?),
at least until they are all laying.
Odd that they won't go into the nests, nest messing has been the number one sign that laying is imminent here, but I've always had adult hens around too. First flock had 5 adult hens and a cockbird, he showed them the nests the first day they are here.
New layer notes blurb:
New layers can be quite goofy acting, they don't know what they are doing at first and can be confused and anxious, it can take up to a month or so before they get it all figured out. Putting some fake eggs or golf balls in the nest might help show them where to lay. They may scratch around in the nests for weeks before laying, spreading the bedding everywhere. They will scratch around a bit less in nest as they get used to the routine. Meanwhile, eggs everywhere, some of them can be rather funky looking, soft or thin shelled, huge double yolked eggs.