It's probably because you cut your calories.
When there isn't much left to lose, the body wants to lose slowly. When you're talking 5 pounds - you should be aiming to lose that over 3 months. A pound every 2-3 weeks is PLENTY fast for the body when it's just the last few.
So set yourself a maintenance level range (as if at goal weight) on Spark. Set start weight and goal weight to the same thing (the lower number) and set your goal date a year ahead. That gives you a maintaining range.
Just eat at the bottom of that range. You'll be eating around 200 calories per day less than you need, and would lose a pound every 2-3 weeks at that rate.
Don't fight it - you can't lose weight fast when there's only 5 pounds to go.