How long has the fish had the white spot on the tail.
You need to improve there diet with more frozen foods like brimestrimp and veg.
Cook some frozen peas for a few minutes, let cool down and pop out of shell. Mush into small peices and add to the tank.
So the cory just bending its spine. its not bent all the time.
The white patches do they look fluffy or just bleaching beneath the skin.
If the they have a y shaped tail it sounds like anchor worm.
Here a pic of anchor worm.
You need to improve there diet with more frozen foods like brimestrimp and veg.
Cook some frozen peas for a few minutes, let cool down and pop out of shell. Mush into small peices and add to the tank.
So the cory just bending its spine. its not bent all the time.
The white patches do they look fluffy or just bleaching beneath the skin.
If the they have a y shaped tail it sounds like anchor worm.
Here a pic of anchor worm.