If you also have a spare airstone and small heater or warm room, move the tetra into the betta bowl. Neon tetra disease is highly contagious if the fish dies and is eaten by the other fish - they'll all be sick in no time so you MUST isolate (seperate) the sick fish from the apparently healthy ones.
A bent spine and faded color is also a symptom of fish tb. The same applies to it though - you'll have to isolate and there's nothing you can do. However, fish tb is contagious - as in humans can get it - so if you have open wounds on your hands or scratches or whatever, don't put your hands in the tank water - or wear gloves! If you see any sign of swelling go to a doctor immediately and tell them you have a fish tank and your fish may have been infected by tb. Don't worry too much though - people rarely catch it and it isn't deadly - just incredibly unpleasant.
Also, how large is the tank, what other fish are in there, is it cycled and what are your water parameters?
In actual fact, you should euthanise the sick fish so it doesn't suffer and the disease has no chance of spreading... Clove oil in a seperate, prefferably aerated, bowl is my preffered and most humane method.
A bent spine and faded color is also a symptom of fish tb. The same applies to it though - you'll have to isolate and there's nothing you can do. However, fish tb is contagious - as in humans can get it - so if you have open wounds on your hands or scratches or whatever, don't put your hands in the tank water - or wear gloves! If you see any sign of swelling go to a doctor immediately and tell them you have a fish tank and your fish may have been infected by tb. Don't worry too much though - people rarely catch it and it isn't deadly - just incredibly unpleasant.
Also, how large is the tank, what other fish are in there, is it cycled and what are your water parameters?
In actual fact, you should euthanise the sick fish so it doesn't suffer and the disease has no chance of spreading... Clove oil in a seperate, prefferably aerated, bowl is my preffered and most humane method.
I don't know what clove oil is... 
