10 pounds in one week does sound like a lot, but I have seen 4-5 pounds in a week with my boxers as puppies.
Spike weighs about 42-45 pounds at 4 months old. You just never know. He recently "shot up" and looked so thin, leggy, now he is filling back in (barely see his ribs), and his legs are thick. His coat has also thickened up and is very shiny.
Just remember, similar to children, they will grow in spurts.
By the way, I am glad the moderator mentioned (above) that it might be a good idea to think about switching to the adult kibble. I did this very thing above 5 weeks ago and the difference is amazing. I completely dropped the brand of kibble that I had used for years (IAMS), and I am actually feeding a cheaper food (with good ratios), and the difference in all of the boxers is wonderful! Their stomachs are settled, their coats are shinier, and they are eating better.
Best wishes!