To help you decide on returning for a replacement or a refund, you should check what results other real-world people are getting. I do this check before buying any lenses.

Google for "flickr pool (name of lens)", or https://www.flickr.com/groups/37412600@N00/ for your Tamron 17-50mm.

Go through the images, looking for non-resized ones with EXIF intact, and wide apertures. If one looks blurry, verify it isn't because they were shooting at a ridiculously low shutter speed, or from noise reduction because they used ISO 6400... rule out the obvious. I find photos of animals good to judge sharpness, because of their fur.