I want to say my youngest was about the same weight at that age. He has always been lean. Right now he is 18 months and 72 pounds. I don't really want him over 80 pounds when he fills out. He is lean and well muscled. A good food is always recommended. Dogfoodadvisor.com is a pretty good site to find one.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD