why are my hens suddenly burying there eggs?

I have 8 RIRS and 2 coops well they usually lay 4 out of 6 in smaller coop, now the past few days all the eggs are in one box in larger coop and buried under the hay and shavings. I did just get 6 8 week old golden comets (they all got loose yesterday and 1 is missing). so is it because I added new hens? is 1 going broody? can 1 hen move eggs out of box and into the next coop? Oh also the first day this happened the nest box (milk crate) was on the ground outside the small dog house coop and the ramp board was down, can a chicken do that? nobody was in there and there isnt really wild life right here near center of town.