I’m heavier than you, but I saw very similar things when I cut out alcohol (I drank a lot daily). I initially saw a pretty dramatic weight loss fairly quickly because my body wasn’t trying to use the empty alcohol calories first and store the excess calories from foods. Alcohol can also stop your body from breaking down fat because it’s busy trying to fight the poison first. I started drinking a ton more water and it regulated itself.
I wouldn’t be very concerned unless it continues on at that rate. Your body should start to stabilize it’s weight loss soon.