Hey everyone...I'm a noob about plants and I bought a pomegranate from nursery few days ago. But today I realized that there are leaves turned yellow and there are black spots on them...:'(

Yet, I saw the roots are coming from the bottom of the pot, does this mean it's root bound? If yes, should I transplant it now or after the treatment of diease?

Can anyone tell me what to do? :'( please help it