Nut is right: If what you're feeding is not enough, increase what you're feeding.

You can add fats/oils too ...

You should also check for parasites.

Many people who say they "worm" their dogs do not do so correctly ...

If you give incorrect dosages of wormers, you've not wormed your dogs at all; you've only built resistance to drugs in the worms they have.

Good luck,

Jack