My puppy is half german shepherd, half doberman, and is will be 8 weeks old tomorrow. But according to her vet visit on tuesday, she's only weighing 3.5 pounds. And she is very tiny. She was the runt of her litter and had to be bottle fed, so I feel like this contributed to her small size, but she also had very bad roundworms. She's been dewormed as of a few days ago, but she's still very tiny. I don't want to feed her extra because I don't want her to get fat, but I do want her to be a strong, big dog one day. Tips?