Thanks, Hoppy. Things have improved with our leghorn. I didn't entirely remove the nightlight, but turned it so it shines at our house (as opposed to directly at the chickens in the coop). The night laying stopped, except for maybe one night egg per week.
I think you may be right about needing to change our nest box. SCG had suggested making some movable nest boxes, to help train them to lay in the box. We put one out in the run, and one up on the roosts. The night layer and the outdoor layer immediately took to the new box up on the roosts, so we left it there. It faces the sunny south windows, but they don't seem to mind that at all.
We now have 7 of 16 who are laying, and only 2 consistently use the community box. We got the design from a website that said chickens do not like to eat in the dark, and that would help prevent egg eating. All of the chickens like going in to check out the community box, but most choose to lay in the one box on the roosts, which was causing a line at the box.
We put the other movable box that had been outdoors in another area on the roosts, and 2 hens laid there just today.
Meanwhile, I like the idea of making the openings on our community nest box bigger. For a while, I was actually wondering if our light brahma could fit through there, she is so big!
(She does fit, though). I'm hoping the community nest box will work out eventually, even if in some altered form. Since they all tend to like to lay in the same box, it would make things simpler if they could all just pile in!