[Crystal R]

I am a new boxer mom. We just adopted two puppies that are roughly 3 months old. They are severely under weight. According to the vet they should weigh some where around 20 lbs. Right now they weigh about 6lbs. The vet said as long as I am feeding puppy food as often as they want then they should be fine. I was just wondering if there is anything else I can do to make them healthier. Any tips or advice?