A 20 gallon enclosure would be too large for a hatchling. You can try to clutter the enclosure with crumbled newspaper or try cluttering it with fake decor plants so there are NO open spaces. How many hides do you have?
85F is too low, Ball pythons need their warm side to be between 88F-94F during the day, and it wouldn't hurt for it to be at night. What are you using to control the undertank heater & infrared bulb?
Ball pythons do not bask, as they are nocturnal and would much rather hide during the day.