Why are there black spots on the wall above the bed in the quarantine hotel?

It’s too humid. If there are black spots on the wall of the house we have just decorated, it proves that our wall is relatively humid, which is why such black spots appear. I think this is because When we were renovating, the wall was relatively humid, and the moisture passed through it. This is because our wall is moldy. If there are such black spots, it is more reasonable to find professional workers to help repair it