You arn't doing anything wrong
The plan works differently for everyone, some people it seems to fall off almost every week, others get slow times now and again.
7lbs in first week is awesome, that's 1lb more than I lost in my first week and you've lost in a fortnight what it's taken me over the last 3 weeks to lose! AND men lose faster than women! So a big well done!
Having said thatm it's best not to compare yourself to others in terms of your losses; everyone is different, has different levels of daily activity, different calorific needs based on musclemass/lifestyle/job etc and different amounts to lose which can really affect how wuickly you lose (more to lose = faster loss generally).
Don't look at other people's tickers and think "oh they lost X this week, I only lost Y..." as that's a surefire way to get yourself down.
Instead, you should be proud that you have lost 2lbs this week.
If you wern't doing LT, chances are you wouldn't have, and who knows, you could have gained that this week had you not started the plan!
You are on target for your 1stone a month, so chin up!
Keep going, once you hit your first stone by the end of the month you'll be over the moon and dying for each day to fly by until your next WI!