I agree with the strip washing first.

I use the Bumgenius 3.0 (not sure what they come under in terms of Pocket or One Size nappies) and all I do is add a booster into the nappy along with the regular insert and DD only leaks if I forget and leave them on her for too long. There is a new version of these which are the 4.0 ones.
I have also discovered she becomes a MUCH heavier wetter when she is teething so maybe there is something else going on?

HTH Nae x