Font size changes after running xrandr --off
You can change the size of fonts for future windows opened by opening the terminal and using:
xrandr --dpi 96
For higher resolution (1920x1080) monitors try using:
xrandr --dpi 144
I use this on programs that do not implement HiDPI scaling themselves. Although it may not explain your problem it may solve it. Or it may not... YMMV.