Manjeet, I've gone through the phase you've been going through. I'd just suggest you to gradually phase commercial food out of his diet and introduce home-cooked food. I'm not against feeding ready-made food to ur dogs but like humans, dog also require variety in their life. How can we expect ourselves to keep having dal-roti everyday? Won't it be montonous and a day will come when we'll refuse to have it completely. Similarly, or dogs require variety in their diet. Just imagine how they feel when they chew those same tast, same colour same size kibbles.
Eggs ( boiled or raw ), meat ( raw or boiled ), rice, yogurt are items on which the entire foundation of dog diet rests. So gradualy intoduce these in his diet and you'll see results soon.