I find mine are a bit stinky during rainy weather coz I dry them on the clotheshorse indoors, or in the dryer. They're usually ok tho after a good dose of sunshine with the next sunny wash.

Have you had them long? You can do a strip wash with bicarb soda and vinegar, but it's not recommended to do a lot coz it ruins elastic etc. But that freshens them up nicely.

Other than that, I've found mine smell a bit if I use too much washing powder. Funnily enough, the less powder you use, the cleaner the nappies are. hehe.