nah, it's normal. As long as it's just a once in a while thing and not something that happens consistently or repeatedly I wouldn't worry about it. If it happens often, then you may need to increase the calcium available to your hens (adding free choice oyster shell or crushed egg shell, reducing the availability of treats so that they are eating more of the layer feed) or you may need to keep an eye out for a hen that looks sickly as a consistent issue with the reproductive tract that might cause shell less eggs could also increase the risk for internal laying. But once in a while is nothing to worry about.