Hello! We have a new 9 week old chocolate lab. We got him at 7 weeks and within a few days he was pretty sick. After a vet visit, we learned he was eaten up with worms. He was on medicine for several days and weight picked up. Then we had another setback and back to the vet we went. He now seems to be in the mend, but seems very small (currently 8 lbs 2 oz) - though gaining and shape appears healthy. He was 4 pounds 2 oz when we got him. Should we be concerned?