I got my seven male Call Ducks a week ago. They are 14 weeks old. They have a large pen and are very active in the pool. They are in coop at night. They don't seem nervous and know my voice. But the food isn't going very fast. I'm feeding them Purina Sunfresh Flock Raiser. And It's in the coop at night too. Roughly how long do you think this 5 lb bag should last? Other tips?