Your body weight and your body compositions do change. It is normal to see your measurements fluctuate. Even within the same day, you may see different results when measuring at different times. We suggest you measure around same time and under similar conditions (e.g., before dinner) to maintain measurements consistent and comparable.
In terms of body fat and other body compositions, different equipment may give your different readings. Better to focus on relative changes of the values measured by a same device over long term.