Tamron 17-50 VC - Sharpness issues around the corners

I have a Tamron 17-50mm VC lens and recently I have noticed that at 17mm wide (VC always on) the corners are getting very rough, and the issue seems to be getting more pronounced than I have seen it before.

Is it just me notificing it more or do you guys think the lens' got actual problems? I know that this lens isn't it's sharpest at f2.8 and 17mm, but my results below seems really bad to me. I shoot in auto most of the time... I wish I could use auto and prevent it from open wider than 3.2 or something at it widest in this mode, if that is the issue.

Notice the bottom right corners: