Humidity should be between 40 and 60% for ball pythons, 80%+ when they are in shed. Twice daily misting and providing a large water dish are the best ways to keep humidity up. Some substrates such as coconut husk fiber will raise humidity, as well spanghum moss. If you have a glass tank with a screen top (those things lose humidity FAST), cut some plexiglass to cover 3/4 of the screen top.

Those waterfalls are meant for use with frogs and some small lizards; they aren't a good idea for snakes and tend to cause issues.