But when I see white bumps, I generally think lymphocystis,
lymphocystis looks like cauliflower and normally spreads all over the body. It doesn't look like a bump.
The fish may just need a break from meds? Perhaps it's just nothing...
If the kanamycin doesn't help, I'd leave it be for a couple of months and see how it goes....Antibacterial meds just reduce the number of pathogens, the rest is due to the fish's immune system to deal with.
Also, if you're still thinking HITH or Hex, alternative treatment is high temperatures, in the range of over 31C-32C ! It can only be done if the fish can naturally handle high temps for prolonged periods. That temperature will also kill true fungus(non-bacterial) If it is bacterial based, high temps will obviously be counteractive.