illness or injury?

Hi! We recently got a guppy and his left fin is looking weird. It doesn’t look like ick but not sure if it’s a fungus/Illness or deformity. Tank is freshwater 20 gal, 79 degrees F, tap water(conditioned), ammonia levels 0, nitrate/nitrate 0 ppm. He can’t seem to move his left side fin and his...

Can anyone help identify what could have killed this blonde Naso tang? He came out of QT medicated with copper and looked beautiful. Took to a customer’s tank and he died one day later snd had these black marks all over him. Anyone know what it could be?