healthy, and yes, get a kitchen scale that measures in units of 1 gram or 2 grams. If anything, it seems to be more on the plump side, definitively not underfed

For young ones, 10-15% of the body weight in food once a week is fine. For adults, if not breeding, and fully grown, you can go down to 8-10% of body weight every 10-14 days. If breeding you need a more intensive gender-specific feeding routine.

But right now based on the pictures i would say all is perfect.