All comments are good & absolutely valid.
1. Deworm immediately- Not matter How good are you feeding them, all is wasted. I know a good tablet, may be some better tablets are available. I found CANGRO good & effective.
2. Multivitamin:- You can take Beaphar's Top 10, very good multivitamin.
3. Calcium:- Lots pf good calcium product are available, but I found 1 good tablet for dogs i.e. IC CAL (its a human medicine), having Calcium & Manganese.
4. Animal Protein:- If can't cook @home then few good product are available @pet shops. Try Jerhigh's Chicken Gravy product (don't opt Chicken with Vegetable gravy), Best is Chicken with Liver gravy...
But best option is Homemade Meat & Chicken (but not spicy & oily).
5. Glucosamin:- Large breed dogs needs extra care for legs & joints. For that they need Glucosamin. You can try Chicken Legs (in summer) or Goat's legs (in winter). Few tablets are also available i.e. Rejoint Tab (having Glucosamin & Chontrodin).
6. Try to eliminate Milk with Curd.