Is my male puppy underweight?

Hi,

Wondering if my about 5,5 month old puppy is underweight. The breeder said the litter was on the smaller size but he only weighs 14 kg and from what I’ve read online he should be much more. He’s energetic and I can’t see anything strange with him. I can feel the ribs if I push through all the fur and I’ve done the so called knuckle test and it feels fine.

Attaching some photos of him to see