Weight loss between feedings

I have a pastel female. When she arrived she was 900 grams. She ate 3 meals (80 - 100 gram rat each time once a week) and when I weighed her after that BEFORE she defecated, but had digested for 5 days, she was 975 grams.

She then went into shed and didn't eat that week, and after shed and defecation, she was 925 grams.
She skipped another week after that, and is today 913 grams.

1) Is it normal for them to lose so much of the weight upon defecation? (No I didn't weigh the feces).
2) Is it normal that she lost another 12 grams in the week she refused food WITHOUT any defecation?

I also have another pinstripe that will eat a meal, her weight will boost up, and then she will stop eating until she loses some weight, and then eat once and it will go up etc. so she is always between 1150 to 1250 grams or so. At 1150 she looks thin. I can't figure that one out. I figures some others out before like the one that didn't eat at all but discovered she only ate mice. This pinstripe I am clueless.

That much fluctuation is pretty reasonable, just visually compare their body size versus the size of their poops and you can tell it weighs a good amount.

If it were my snake I wouldn't worry at all, at least she's eating. If it were to continue for months on end where she was eating yet still losing weight then I'd be concerned.

Their metabolism is nothing like a warm blooded animal, so slight changes aren't anything to worry about... my baby dumeril's boa didn't eat for an entire 7 months but only lost 4 grams total so its not really that big of a deal.