Why are my little one guinea pigs so small?

I have two female guinea pigs born around August 25th. They've become good pets of mine [I also own their parents, everything next to them is fine], but they are about 3/4 the size of the ones I see in pet stores.

They have grown significantly since birth, but it worries me the Mill-pigs are larger. I nurture the kids good food [salads, carrots, pellets, and hays.], so I doubt it's that.

Thanks.
Answers:    The ones at the pet shops might be elder than yours that's probably why they are bigger than yours. Unless there is a sign saying how old the guinea pigs at the pet store are, you probably can't find out how ancient they are so you can compare the sizes. Also a lot of times pet shops overfeed their animals, that could be another reason why the guinea pigs are bigger than yours. Since your guinea pigs are only roughly speaking 3 months old, they will get bigger over time. I would worry around it. Also not all guinea pigs are mill-pigs just to let you know. Many local pet shops that aren't chains, breed their own and don't over breed them.
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