76* is a little bit cool for a cool side. Ideally, you don't want any night drop in temperatures. If you need the bulb to keep your ambient and cool side temps up, then use a red bulb or a moonlight bulb so you can leave it on 24/7.

Also, what kind of thermometers are you using? If you aren't using digital thermometers with a probe then you aren't getting an accurate enough reading. Many newbies are tricked into buying those round stick on gauges which are not accurate enough. Also, many newbies don't realize that they need a thermostat in conjunction with the UTH. If your snake is favoring the cool side, then chances are it is because the hot side is too hot, or they don't have identical hides.