60 Gallon Tank Anyone know what’s wrong with my cherry barb?

[StoneSatsuma]

My barb has been like this since the morning. He’s really wide, like his body has swollen. Since the picture, he can’t stay upright and the his scales are pointing out a little bit. I was worried he may have pine coned but they seem more inflamed than pine cone(it’s not as bad as pictures I’ve seen online). Anyone able to help?
Ammonia 0
Nitrites 0
Nitrites 20ppm

 

[N13]

maybe he has swim bladder? Try quarantine... I have not seen this before so I can't really help you, sorry!