Be careful with cat and dog foods. They are super high in sodium. Not something you want to feed very much or very often. I would go with canned tuna personally.
I have mine on flock raiser all year long, it already has higher protein and they come through molt just fine. I would also be leary of giving them food designed for another species. Nutritional needs vary so much across species. Of course, my chickens are all over my spilled horse grain every morning. That hasn't done them in so far, but it could.

My two Sebrights that have finished their molts look FABULOUS! Poor Frannie, the last of the silvers to molt, is bare all over! Looks like someone tried to pluck her. A couple of my barreds are going into molt as well, and both of the remaining sexlinks have bare shoulders. And then there's Frou-Frou--she has enough pins all over she actually doesn't want her visit right now! :/ My poor baby!