Yeah I think so, I was worried the one week when I only lost 4lbs but the next week I lost six and the week after I lost 8. So I think its just one of those things. Good luck for next week.
3-4 lbs is a very good loss, and as you start to lose the majority of your weight, you will average out at 3-4lbs and you'll even have some 1lb a week losses, don't let it dishearten you!