I have always believed that columnaris has the following symptoms.
White spots on mouth, edges of scales, and fins
Cottony growth that eats away at the mouth
Fins disintegrate beginning at the edges
'Saddleback' lesion near the dorsal fin
Fungus often invades the affected skin
Rapid gilling in cases where gills are infected
Most Columnaris infections are external, and present first as white or grayish white spots on the head, and around the fins or gills. The lesions may first be seen only as a paler area that lacks the normal shiny appearance. As the lesion progresses it may become yellowish or brownish in color and the area around it may be tinged red.
Lesions on the back often extend down the sides, giving the appearance of a saddle. On the mouth the lesions may look moldy or cottony, and the mouth will become eaten away. Fins will erode and have a frayed appearance as the infection progresses. The gills filaments will disintegrate as the bacteria invade them, and the fish will begin breathing rapidly due to lack of oxygen. Less commonly, the infection will be internal, and display no external symptoms.
I am not say this is not a possibility and I will keep an eye out for other symptoms, but usually it is caused by slack tank maintainance or introduced by unquarantined fish. Which in this case would not be the reason as I am almost obssesive about WC and other maintaince and have not introduced any tank mates for quite a while.
ANY OTHER POSSIBILITIES??