The second photo has some areas where the focus seems fine. For example, the dots on the rightmost egg look pretty sharp, and a lot of the nest looks good.

The biggest problem is that the eyes aren't sharp, so I think you just missed the focus here. Perhaps the subject moved after you focused? Perhaps he/she moved during the shot? Babies are tricky that way.

Another possibility is that your lens is just a lot softer at the wide end than it is at the long end. In fact, the more I look at the second photo, the more it seems like the lens might be the problem. Do all your photos at this focal length and aperture have the same issue? It doesn't look like motion blur, and shooting at 1/160s at that focal length should be fast enough to prevent that anyway. The first thing to try is a smaller aperture. Try a similar shot at f/5.6 or f/8 -- lenses are usually sharper when they're stopped down a bit instead of wide open. If that solves the problem, then either live with not shooting wide open at the wide end of the lens or consider other lens options. Nikon's AF-S DX NIKKOR 35mm f/1.8G seems to be both well regarded and inexpensive at about $175.