White bumps that don't seem to affect the fish in question could simply be tumors, yeah. They're usually genetic defects but occasionally caused by viruses. A tumor isn't a reason to put down a fish unless it seriously affects quality of life (fish can no longer swim, eat, etc.) or if you have good reason to suspect a virus and want the fish out of the system. I'd be more likely to move the fish to a hospital tank for observation before doing that, though.
The hatchetfish looks like it may have a bacterial infection. If I had to take a wild guess, maybe some type of Aeromonas infection? An antibiotic like Oxytetracycline might be worth a shot. The main treatment for such infections is good water quality, proper nutrition, and lots of water changes. Antibiotics should be used for more stubborn cases. Maybe test your water just in case something is off (by now you probably knew I was going to ask about water parameters at some point, haha).
More photos from other angles would help but I know how hard it is to photograph fish. Does the hatchetfish have any other symptoms?
The hatchetfish looks like it may have a bacterial infection. If I had to take a wild guess, maybe some type of Aeromonas infection? An antibiotic like Oxytetracycline might be worth a shot. The main treatment for such infections is good water quality, proper nutrition, and lots of water changes. Antibiotics should be used for more stubborn cases. Maybe test your water just in case something is off (by now you probably knew I was going to ask about water parameters at some point, haha).
More photos from other angles would help but I know how hard it is to photograph fish. Does the hatchetfish have any other symptoms?