Classic Responsive Template in landscape mode on iPhone6s ( and iPhone5) switches to two columns but runs off the bottom of the display rendering it useless. Should be able to remedy this in css but how??

Should one not be able to narrow a window on a browser and have it "Jump" from 4 to 2 columns without all the display contortions in between?

Test Site With The only mod installed is the Column Grid Layout.
http://pcsnnets.com/tp18

Any suggestions are welcome.