yes that is common at least with my girls it was, when they are starting to lay this may happen a couple of times and yes it does mean no egg tomorrow, i have seen them lay the second soft shell egg before and it looks very painful for them so if you see a girl that is very reluctant to move has a very blank look on her face and if u see her with her tail pumping she may be laying a second egg. my girls never laid their second egg in the nesting boxes, they always laid them outside because they knew it was a bad egg. all it is is tomorrows egg coming out early, and it should fix itself when the hen gets on a regular schedule for laying her eggs, it shouldn't be anything to worry about unless if it happens very frequently.