i meant double check your room temp and your cool side temps.
usually my cool side temps are within 1 or 2 deg. of my room temps. ( if your room is 84-85, would not the cool side of your tank be close to that and not 77) it doesn't hurt to double check things. i'm a hvac service tech and i check temperatures all day long and i still double and triple check my cages every day and night. my opinion is that if your cool side is 77 your ambient room temps are close to that. all this aside somethings to try to warm up the cool side might be to decrease ventilation, cover up the screen top. i think 76-80 for the cool side is ok, provided your snake goes to the hot side to warm up. make she it is not choosing the cool side all the time for security reasons. provide multiple hides in both hot/cool sides, snakes will choose the temp they need if everything else is in line.

hope this may help

thanks

vaughn