Hi, I ordered six ducklings from Metzer and one arrived dead. I was sent a replacement and her buddy the following week. When will the older ones and the younger ones be the same size and when will they work together? I let the two little ones out with one bigger one and the bigger one chased the little ones around and tried to bite them. On Monday, the bigger ones will be three weeks and the younger ones will be two weeks. I know I'm not the only one that has been sent replacements; what do you guys do? Even if they would work together, I'll probably keep them separate until the little ones are bigger so they don't get stepped on or something like that, but, since I don't have a limitless amount of time, it would be handy if I could let them all outside or in the tub at once. Thanks