desktop scaling issue

I have two computers, a desktop machine and a laptop. I have kubuntu 15.10 on both of them. I have configured them identically. I have an Nvidia GT650 in the desktop and GT650m in the laptop.

I started using the laptop at work and plugged it into two monitors and disabled the laptop screen. When I did that, it seemed that the images on the two external monitor screens were larger than they should be, about 33% larger. The screen on the laptop is 17 inches and goes to 1080p. The desktop monitors are all 1080p monitors. When I check the monitors, they say that they are being driven at 1920x1080. The control panel says that they are at 1920x1080.

I have two images that shows the Settings tab in chrome on the two computers.

Laptop http://imgur.com/eCTnoXo

desktop http://imgur.com/lRd8Qwb

Is it possible that I have tweaked a setting somewhere to cause the laptop to scale things up? The control panel at System Settings -> Display and Monitors has a scaling sub panel, and the slider for that is 0 (far left position).

Thanks in advance.