If you are in ketosis then it means you are burning fat - though it may be primarily the fat you are consuming in your diet. But you are not laying on new fat. You have been so calorie restricted that your body may well have sacrificed a lot of its lean muscle tissue in order to suppress your basal metabolism and your body took all kids of steps to suppress it further. Now that you are taking in enough calories (at LEAST 1500 kcal per day in your case) you body may be trying to restore some of the lean muscle it has been foregoing for a long time. That will add lean body weight and may well cause weight gain as the various players vie for the overall effect. But more lean body mass means a higher metabolism. At some point, you will fall over the edge as start seeing obvious progress.

It's good to hear you have started a journal. I'll try to visit it shortly. Have you taken your measurements yet?