Don’t despair Clairy, our bodies fluctuate so much from day to day, that is the danger of daily weighing, it can demoralize you wrongly.
I think the lower water intake made a difference, it is such an important part of BSD, success..I know it is hard to drink that much at first, even now I find myself slipping, and not drinking enough some days. How about filling litre bottles and leaving in fridge, ice cold, and try to get through at least 2 a day. You can count your teas/coffees as well of course. It’s another new habit to get into. Lots of changes in lifestyle with BSD.
Keep going, make sure you are properly weighing and not guessing amounts. It WILL work for you.x