bent dwarf gourami

[san1belfish]

i have a 20 gallon tank that i have 6 tetra's in. i had to put 2 dwarf gourami's in the tank as they were being harrassed in my 100 gallon tank. they have been fine for months, however, one of them now appears to be bent like this ~, None of the other fish show this condition. The fish is acting normally, eating, hiding around plants etc.
my water conditions are fine. 0 ammonia, 0 nitrites, less than .4 nitrates, ph 7.2, temperature 80. any ideas? thanks much

 

[MyCatsDrool]

tuberculosis?