51's a weird yeast, Generally catch sour cherry in the aroma depending on fermentation temp. 2 weeks is pretty fresh for that yeast, give it at least 2 more weeks, ideally 4-6 at a nice low lager temp to clear and clean up. I'd also recommend a diacetyl rest.
personally I've used it twice and found it to have a bit too much sulfur. I prefer 090,060blend,or001 for clean fermenting yeast, in that order.