Flock Raiser has worked for my ducks. They do enjoy/need things like grass and bugs though in addition. They get those things by free ranging or if that is not possible in your case, take it to them. Cut grass or just give them the lawn clippings (no chemicals). A night light near where they spend their nights will bring the bugs to them. Some grit to help break down the grass and bugs. Scraps from your garden and kitchen make a nice addition to their diet also.
That said, flock raiser is now different than it was. Land of Lakes bought Purina and flock raise looks and smells different. It absorbs water different also. This happened only a month or so ago, so I am not sure if it will be good or bad, but it is different.