I know this sounds silly. Especially since I'm not experienced in this area, but when we washed our fellows too much, it striped the oil and they smelled. Could it be bathing everyday?
What we do now is blow the coat out with a high velocity dryer twice a week in between our actual bathing. They smelled much nicer afterwards too.
When I feel it's necessary, we use a sprinkle I make that is aromatherapy and made with arrowroot powder, powdered herbs, and soda. I just shake it into the coat, and massage (you know how the newfie skin just rolls back and forth?), and get it all over as best as possible, then leave it for about 15 minutes, and blow it out with the dryer! Works wonders and they like it too. I use this once in awhile, probably only once a month. It probably isn't really necessary, but we have found it also helps repel other things they may react to like dust mites, other mite things we cant see, and so on.
Luv