Ash (aka Aquila) is having troubles posting so she asked me to post this on her behalf:

Glad to hear he's eating, even if lightly!

Curved spines can be due to illness. We worry about other causes, like
fish TB, when there are other symptoms of that disease, along with
curvature present outside of illness situations.

It sounds as though you'll have to do 2 treatments with the meds.