Congratulations on losing 10lbs. in Week One and for your success in losing 50 lbs!!!! That is a great accomplishment!!!
Often when we start a new program, there is a bigger loss right at the beginning from new eating habits.
Please don't be discouraged. Don't expect to lose 10lbs. every week - it simply isn't possible. Your body is probably adjusting to the big loss from the week before. A healthy normal weight loss is supposed to be 1 to 2 lbs. per week.
The biggest mistake I have made in trying to lose weight is getting discouraged from week to week and simply giving up. The result for me would be to gain even more weight. Each week is going to be different so hang in there. This is a long process so just stay on your program and keep going!