Our black star started laying about a month ago and for three weeks we got large eggs like the one of the right (regular grocery store size). Then all of a sudden we got mega-sized eggs (can't even close the carton lid) for a few days like the one on the left. Now they seem back to the original size. Is this within normal hen abilities? Or, is that giant buff orpington that we can't decide is a rooster or a hen sneaking in giant eggs?