Our sprocker bitch had pups in November last year- she had 4. There was a bit of difference between the pups' weight but as long as they are all gaining weight then I wouldn't worry about supplementing feeding. Use the milk replacer when you start to wean, we found Whelpi really useful then. I didn't weigh ours every day, more the day after they were born, then 7 days, 14 days (for worming), 5 weeks, 6 weeks and 8 weeks before they left.