It's fungus and is not uncommon in fish that have been stressed over the winter. Sometimes only a few fish will have it, sometime lots.

Did you have any oxygen problems this winter i.e. lot of snow cover? Did you do any catch and release of you bass this fall when temps were under 50 F. Or did you overmix you water column this winter? Fish overcrowded?

If none of the above I wouldn't worry about it as occasionally some fish just don't holdover the winter as well as others. If you did have problems you may see more of this as the water warms up and bacteria takes advantage of the fish.

Fungus is typically a secondary invader of weakened or injured fish. It depends on how severe it is on whether a fish will recover.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.