I was able to speak to my puppies breeder tonight. I didn't not get him directly from her so I didn't know this when I got him. Turns out he was not only the only Black and Tan in the litter of (I think she said 9), but also the runt. He had some immune system related health issues but seems to be back to normal now. What should I expect as far as growth and development? Is there anything I should be doing? He's about to be 20 weeks old and weighed in at 27lbs at the vet this past Thursday. Anything I can do to help him grow and mature into a normal weigh and size? Or is he always going to be tiny?