Hi, am having a little problem with my temps for my beardie,hes 4 years old. Ave got a 4ft long/1ft wide/1.5ft high viv. Am currently using a 100w basking bulb (exo terra) not a coil. My basking spot is at 99f and my cool end is 78f. A cant seem to get it any higher? The probe for my thermostat...