Fungus on my Bulb. Medusa?

[Cymbaline]

These yellow and black spot appeared rather quickly. When I first received the plant last week it had some black spots but I didn't want to worry. I kept it away from my other plants and yesterday I found the leaf like this.

I just want to confirm. I think it maybe a type of fungus? Should I cut it off , just soak it Physan?

Thank you