She looks very healthy to me, and gorgeous! Usually I know my bp is about to poop because it looks like her tail is super fat at the end, but on the underside.
Your bp might not be ready to poop yet I think. I would just watch and wait.
In terms of the drastic weight change I wouldn’t sweat it. She could be very much growing and hit a growth spurt, as dakaki has said, or the lack of defecating may contribute to the weight as well. You have various factors, so I’d wait and see.
She looks healthy so I wouldn’t be too concerned.