Not even 1 lb!

I think it's related to the exercise. I am doing JM 30 DS and the scales didn't budge at all for the first 15 days I was doing it. As soon as I took a few rest days, there was a big drop. I don't think it can be muscle in that short space of time, but some people have mentioned water retention increases when you exercise a lot, something about your muscles storing water to repair better? I don't know much about this stuff, but it makes sense with what I've experienced.

Just keep at it.