On a full wash use full amount of Canestan, and an extra hot rinse.

Strip wash will get rid of the build up on the fibres int he cloth. Hot wash and a couple of drops of washing detergent, and an extra rinse should do it. If you use washing powder like Omo or Drive, etc you should do a strip wash every 4-6 months or when you notice th nappies becoming less absorbant. If you use bicarb or mineral detergents like EcoStore etc then you don't need t do it as often I found.

The Canestan though will kill the fungus. Also, Lavender oil is ace for that, a few drops in the rinse cycle every wash will help keep it at bay.