Frustration central

I have been on a weight loss journey for the past 2 years. I have been doing FB workouts the while time and the results have been fabulous. Nutrition wise I have cleaned up my eating slow and steady and the results have been phenomenal. I started at 78 kilos and at the moment I am hovering around 51 kilos. In the last 2 weeks I have been extremely frustrated because I have seen my weight suddenly shoot up a kilo and I have no idea why. I am saying this already considering the hormonal weight gain and what not. This mysterious kilo is making it impossible for me....pls help