Your poor hatchets are under considerable stress from several things, one of which is being only two in number. Hatchets are, like almost all characins (tetras, hatchets, pencilfish), shoaling fish that live in large groups. A minimum of 5 but preferably more will allow them to interact and feel "safe". Shoaling fish that are alone of only 2 or 3 feel constantly under threat because their natural instinct is to be with a group for security and interaction.
I don't know which species you have, there are three genera and the species in Carnegiella are smaller and 5 or 6 would be OK in a 10g, but not with any sort of predator fish/crustacean that adds more stress. Try to imagine how you would feel day after day if you had a bully standing outside your house and following you everywhere; even if he never "attacked" the fact that he is constantly near is enough to keep you in constant fear and stress. And in fish, stress leads to innumerable health problems and guaranteed shorter life--not any different than in humans actually.
None of us can just buy a fish we see and thinki is "neat", you have to know the fish and what it needs to be healthy, and be able to provide that as a responsible aquarist.