Swim bladder can look like the fish tail is weighing them down in the water.
Bent spine can be old age, injury, birth defect, internal parasites, fish tb, vitamin deficiency.
I would issolate her till we know what caused the bent spine.
Is her anus enlarged or red and inflamed.
Do any fish look thin or bloated.
What does it look like when your fish go to the toilet.
Any worms prutruding from the anus.
Check all fish for those symtoms.