This is common when you plug an HDMI connection in. I am going to try and do my best to guide a fix in for you but as I do not have an HDMI connection myself, I do not have the screens in front of me.
You have to access the Additional Settings section of Crimson to resolve this.
1. Right click desktop, go to AMD Radeon Settings.
2. Click on the middle icon labelled DISPLAY.
3. In the upper right hand corner, select Additional settings.
4. In the new box that pops up, you should have an option on the side that will allow you to change the scaling of the display. It will either be under HDTV support or Properties (Digital Flat Panel)
I had to do this with one of my old hdmi displays because the blur was killing me. I hope this helps!