My rouens are 5 weeks old, some of them are huge, while others are half the size. Is this normal? 3 of them are the size of the smaller one in the back, two of them are huge (front ducks) and one is halfway in between the two sizes. The larger ones are also feathering out sooner, but are also more lazy, the smaller ones are very active always bug hunting. Would this account for the extreme difference in size? Or is there something else going on? They are eating non medicated chick starter, plus all the bugs they can catch, grasses and greens in thier run, and ocassional weeds and greens from the kitchen and garden.