Both My Guinea Pigs Are Underweight?

[Turtles]

Now that I have a better vision on my piggies their whole daily routine I decided to weigh them, and they both come out on the low side of their age group.
Panda is supposedly from 3/9 that makes her over 3months but she only weighs 388 gram (0.855 lbs) which according to the chart i got, is severly below what she should weigh ? She eats all the time, if anyone is eating all my veggies for sure it's her! They get Carrots, endive, kale, apple, orange, cucumber and tomatoes (next on my list to get is bell pepper!). Apple, orange and cucumber only every 2days, and only one fruit at a time (so either apple or orange)
Second is Lemon who is 304g (0.6702 lbs) now Lemon is a lot younger than Panda, but I didn't get a clear age. I'm guessing her between 4 and 6weeks (she is also an alpaca, but her hair is still incredibly short which gives away the fact that she's pretty young)
Is there anything i can do to make them gain weight ?
I think y'all already know i'm a bit of a worried Mama, Panda less as i see her all the time and i know she's a real good eater, but Lemon barely shows her face, when she does she's eating very well but she still worries me a tad

 

[EmilyK]

i have a piggie called Oty who is 856g (he's going to be one in a week) and he is severly underweight as well! I've seen that **pea flakes** are a fatty food which increases their weight but not by a lot.

 

[Wookey78]

No advice from me but one of mine only weighs 300g on my scales 400g at the vets. She is tiny compared to her sister. She does seem to eat and I hand feed her a bit but she loves hiding away too compared to her porky sister.

 

[VickiA]

The advice to all members who have concerns about their piggies' weight or any other aspect of their health is to get them vet checked to ensure there is no underlying health or dental problem. Please get your piggies vet checked.

 

[Wookey78]

Mine is under the care of the vet currently