Ball pythons naturally live in sub-Saharan Africa where humidity on average is above 70%. 50% would be pretty low humidity. I'd aim for 65%+ (higher is fine as long as the enclosure isn't constantly WET because wetness+high temp = bacteria growth == scale rot), reading with a digital hygrometer (analog/dial ones are inaccurate). Also, avoid reptiBARK. Reptichip or another brand like Prococo is the one you want to go for if you want to go with cocochips. EcoEarth alone is also not suggested, but it's okay if you mix it with something else like Forest Floor.
Tanks are fine and, like tubs, may need their own adjustments (the main ones being covering 3 sides with wall decor/paper/etc. to make the snake feel less exposed and covering most of the top with foil to stop the heat and humidity from escaping). Tubs can be easier to maintain heat/humidity in, but people often forget that tubs are very sensitive to their environmental temperature, so sometimes they do need adjustments, too. Depending on her size, you may either need to upgrade the tank size or downsize her hide size. Ideally the hide should be large enough for her to fit snug but not too small where she's trapped (so open-bottom is best). That would be more ideal than giving her a smaller water bowl, especially if your humidity is already low (more water surface = more evaporation = more humidity).
Also, when you say heat lamp, do you mean those red heat lamps? Those are good for heat, but because they give off light AND heat, that means you can't turn it off at night so the snake is getting 24/7 light exposure. If that's the case, I would look into switching to a ceramic heat emitter as those give off heat, but not light.
Here's a quick/dumb drawing I did for an example of what to aim for lol

And a friend's actual tank for another example

And just extra visual for what to aim for in regards to temp/humidity. I made this because people often confuse ambient vs surface temperature, but it's a good visual of what to aim for in regards to a temperature gradient and such.

Drag to new tab if the images are too small. :)
-fireflii