It's really simple science. You must simply increase calories. What you are feeding is fine, you just need more of it.

I'd like to share some observations I've made since switching. I've been doing this about 8 months now and have a system I like a lot and is working very well for me.

I feed a concoction I call "Guts". It is a mixture of Chicken Livers, Gizzards, Raw Eggs, Yogurt and Oil. I feed "Guts" every other day typically. There were times when I would go several days without it. The mainstay was chicken quarter per dog. B/c the quarters are cheaper per pound, I would try to bump the weight gain and such by adding more chicken, b/c it was cheaper. Didn't work. I add back my "guts" and their body weight goes up quickly. Lots of calories in this mixture.

What I do now, is I feed "guts" 2 days on, 1 day off and they get a chicken quarter every single day.

With what you are feeding, I'd say up the fats/oils for sure. The Chicken and Rice won't do a lot for adding weight. You may just add yogurt for the calories and get good results.

Best of luck!