Diet, and your socket (amps)
I hope I am not jinxing myself here.
This past summer we made the choice to ATTEMPT to eat no fast food, no processed foods, nothing pre prepared. It is hard, and by no means have we cut it all, all of the time. I did note shortly after doing so that my residual started doing a LOT better within my socket. To explain, I wasn't having as much volume change and particularly wasn't having as much issue with sores or lesions. We moved in August and for the entire month we moved followed by the next three months of hard, hard work and LOTS of fast food. My leg immediately "revolted" and actually led to a sore that took me off my feet for about six weeks. I have since become very strict about the diet, not even affording myself a meal out at lunch. I have noted, once again, an almost immediate change for the better in how my prosthetic fits and feels during the day and have (luckily) not had any skin issues in spite of being on my feet six days a week.
I am not eating with "lose weight" or "super vegan powers" in mind, only eliminated processed foods where possible. IE, we get whole chicken parts, roasts, etc. and cut them into what we want. Mostly fresh vegis, and things of that nature. I feel pretty sure that the salt content alone has a lot to do with it, but wondered if others amps were doing similar and what your results have been.
I've been an amputee for 40+ years, and I don't have much volume change during the day.
It sounds like you may be more sensitive to sodium. If you are sensitive to sodium, then I can certainly see that leading to volume changes.
Changing your diet now may prevent your getting pre-hypertension, followed by hypertension. My husband (not an amp) is 50+ and he's on a low dose of an anti-hypertensive drug. His blood pressure is in the "borderline" range some of the time. Apparently doctors want to treat that, because they don't like it when their patients have a stroke.