My Two Guinea Pig Sisters Weigh Completely Different Amounts; Is This Normal?

[Zerlina]

My two guinea girls are about 4 months old. They are both looking well and eating well, but one of them weighs 534g (about 18 oz) and the other weighs 310g (10 oz) They are sisters and supposed to be the same age; is such a big difference normal? Are they both within reasonable limits? I'm a little paranoid about weight/health now because we lost Teddy (the third sister) over the weekend and her weight loss was really quick. Olga is a quieter guinea pig, but she always has been. I worry that Lol is a (lot more) dominant than Olga and she's not getting everything she needs. Nobody told me it would be this worrying to have little piggies!


You can see how much bigger Lorelai is here. She's the one on the right.

 

[Swissgreys]

310 grams sounds low for a 4 month old, but how long have you had them and where did they come from?
Are you sure they are the same age?
And what are their previous weights like?
My crew of 3 started off at wildly different weights (one of our girls was the runt) but after 2 months at home they are settling down nicely, and are now all within 100 grams of each other.
I do weight weekly, but try not to panic when one only gains a few grams.
Overall if they are going up, and seem happy, healthy and active then I figure they are ok.