40% isnt too bad but what are they house in? first of all you have to keep them seperated/housed apart . . . if they are housed in a tank then there are a few things you can do to up the humidity:
1. cover more of the tank top . . . towel, shrink wrap, etc.
2. place the water dish over the under tank heater(if u have one, if u dont i suggest you get one)
3. avoid using heat lamps they tend to dry out the air and ball pythons need belly heat anyways

but definately get them out of the same enclosure, especially if they are both males(which i think i read)