What a shit week it was.
There is. Since Superhumans are constantly adapting to both the power and their surroundings and thus to how they use their power, it stands to reason that you can screw up your progress, like Ella did.
We are not sure of the exact mechanism, but with the trials, there seems to be a 'right' path and while that doesn't necessitate a 'wrong' path, it implies that Superhumans can adapt in ways their ancestors would find undesirable.
It's especially the talk that Superhumans have the potential to outgrow their monster parent. To me all of that is just a lot of implications to talk around the actual situation.
Here's the deal with other ways to gain power: we've been doing that since the cafe scene. Eat people, monsters, parts, memories.
Honestly, Nico explaining her specific way of powering up kind of makes it clear that those pathways are very personal and depend heavily on the parentage of a given superhuman.