Clearly the image is underexposed. In the evening f6.3 doesn't leave you with much scope. So zoom out and use the widest aperture of f5. That would have helped you a little bit with the ISO.

Zooming out is fine as now the front paw is cut. You have to take chances with slightly reducing the shutter to 1/125 seconds or so as your lens is supposed to have image stabilisation. However, I am not sure how good the Tamron's VC is. Thanks for sharing.

Cheers,
Sabyasachi