That would be water loss due to the fact that your body no longer has to hold on to so much water now that you are eating so much better. I believe that with high sugar/insulin levels, your body needs more water to dilute it all. At least I think that's how it works.
That is good. But don't worry, your fat will start coming off too now that the body doesn't have as many carbs to burn. Losing the extra water is one of the first signs that your body is converting to burning primarily fat.
I never bothered with daily weighings myself. I weigh myself once a week. That way, I never get discouraged with daily ups and downs. Your weight can fluctuate by several pounds from day to day but over the period of a week, it all smooths out.
I agree on not weighing daily, but I was so disappointed yesterday to register no weight loss after a whole week of folowing this regimin to the letter. I won't weigh again until next week, to be sure, because I am well aware of daily fluctations and how focusing on them can defeat your whole purpose.