Bent Nenon Tetra

I have a pair of Neon Tetras in my tank for about 6 months. They have
both grown considerably and they appear to be healthy except for one
of them seems to be "bent" behind his belly. Its body does not run
straight anymore. Right behind its belly the body has a distinct bend
that goes out and then comes back again.

He seems otherwise normal. The tank has 2 clown loaches, a pleco, 2
guppies, and the two neons. Has anyone seen anything like this
before? Is this the "Neon Tetra disease"? If so, will it affect any
of the other fish?