
That sounds plenty. A smaller puppy can't put on as much weight as a bigger pup, but will put on the same amount as the big one did when it reaches that weight.
Puppy weights I have found can vary quite wildly from litter to litter as long as they are gaining and the rate of gain increases as they grow then things are fine and by 12 weeks I have found most pups weigh within 2 pounds of each other in my breed (which are 20 - 23kg adults).
It is always a good idea to plug in small pups onto the milk bar any time you pass the whelping box, even if you have to wake them, so they get more time suckling as they can't get as much in one got as the big ones, and always put them on the best teats, taking a fat one off a teat they have started running well.