I agree with Ash, Debs. Fish TB is not all that common, while many other illnesses are and can still display the curved spine. Think of how when we're ill... we sort of hunch over b/c we're not well... this may be a similar physical reaction for fish when they're ill. The other symptoms of fishTB that we commonly see in fish is wasting away and fading colour. These symptoms coupled with the curved spine and other more classic symptoms of illness like lethargy, lack of appetite... can lead to a fish TB diagnosis... but we never truly know unless a fish autopsy is performed... that will 100% confirm it. One member that I'm aware of here has gone this route to confirm the fish TB diagnosis (through a vet, I believe).

Fish TB doesn't respond to any medication we know of... so IF fish TB was an issue... yes, they would eventually die from it... but some can live months just fine.

Since the others are not showing signs of illness... I would just treat the one that is showing signs. The other fish's immunities are perhaps stronger, or this particular fish was stressed in some way to open itself up to illness. Treating the others not showing signs of sickness could develop into antibacterial resistance if/when they do need to be treated.

Let us know how he responds!

Michele