Sounds like it! Try blocking off the nesting box at night with a piece of plywood, cardboard, etc. Breaking that habit will usually result in cleaner eggs.
Have you tried placing them on the roosts repeatedly after dark? I had two young pullets that would not roost, until after several days of me picking them up and placing them on the roost bar each night.
That said, my winter bedding is usually alternating straw and pine shavings. I use...