It's really hard to judge a beer at this stage, just because you are smelling something out the airlock,
doesn't mean it is actually IN your beer, it may simply be going out the airlock, like Rhino farts or sulphur smells given off by lager yeasts or the making of apfelwein. They don't actually stick around.
Also, it really is hard to judge a beer until it's been about 6 weeks in the bottle. Just because you taste (or smell) something in primary or secondary DOESN'T mean it will be there when the beer is fully conditioned (that's also the case with kegging too.)
The thing to remember though is that if you are smelling or tasting this during fermentation not to worry. During fermentation all manner of stinky stuff is given off (ask lager brewers about rotten egg/sulphur smells, or Apfelwein makers about "rhino farts,") like we often say, fermentation is often ugly AND stinky and PERFECTLY NORMAL.
It's really only down the line, AFTER the beer has been fermented (and often after it has bottle conditioned even,) that you concern yourself with any flavor issues if they are still there.
I think too many new brewers focus to much on this stuff too early in the beer's journey. And they panic unnecessarily.
A lot of the stuff you smell/taste initially more than likely ends up disappearing either during a long primary/primary & secondary combo, Diacetyl rests and even during bottle conditioning.
If I find a flavor/smell, I usually wait til it's been in the bottle 6 weeks before I try to "diagnose" what went wrong, that way I am sure the beer has passed any window of greenness.
Lagering is a prime example of this. Lager yeast are prone to the production of a lot of byproducts, the most familiar one is sulphur compounds (rhino farts) but in the dark cold of the lagering process, which is at the minimum of a month (I think many homebrewers don't lager long enough) the yeast slowly consumes all those compounds which results in extremely clean tasting beers if done skillfully.
Ales have their own version of this, but it's all the same. Time is your friend.
