Weight gain in females with eggs

So I’ve had my first Lock recently and today I reintroduced the pair together in hopes of getting another. A breeder friend of mine said to continue until I notice signs she’s with Eggs. While I can’t feel anything in her belly (yet) and of course no pre lay shed has happened… I was wondering if there was a weight gain that would occur that could also be an indication of her being with eggs.

The reason I ask is because she jumped up 20 grams of weight in one week which admittedly, for a Corn, doesn’t seem like a lot considering I feed her much more often than my males an appropriate sized rat.