What sort of liners are you using??? You will need to NOT use the ones that look like Chux, the commercial ones.
Best bet is going for a raw silk or a microfleece liner with creams.

The other thing is make sure you are using an anti fugal on your nappies EVERY wash, and in the strip wash, also you can use a lavender or tea tree solution with your wipes at every nappy change with bubs, this will kill the fungal infection causing the nappy rash and is a lot better for bubs skin that that hideous cream from the chemist. \

Also, stop using the powder, it will be making the problem worse, and is incredibly bad for girls.