have you tried treating it with fungal cream? The only reason I suggest it is we have been getting horrible blisters looking things which are white and even excema looking skin in places, at first I thought it was the wraps rubbing in the same area for the excema type skin. But after 2 days of applying daktacort (don't know what it would be called in Oz, but it is sold for atheletes foot etc with 2% something and 1% something if you don't get a prescription for it and is the same thing) and a layer of bepanthen (or probably any nappy cream on the top) it has started to go down. I always keep washing my nappies at 60 degrees as fungal seems to be reoccuring with Ben's bum, and we are literally slapping it on at every change, some of it has gone, some hasn't, but it will be about another fortnight before we start easing up on the creams. I am also making sure I am rotating the types of nappies next to his skin, so have found simple g diapers a godsend at first to clear up some places.
Have you looked at your machine instructions to find out how much water it is using - it probably says, and perhaps try a double wash all the time?