New construction before acceptance, wall mold

Hello everyone,
my construction project is progressing well. The screed has been in for almost 2 weeks.
Yesterday I noticed that on one wall (south-west side)

There are 4 spots each about 30 cm long. It looks particularly bad in the middle. I am sending you two pictures of it in the attachment.
For your information: after the internal plastering, it was not easy to ventilate. The external plastering was also done during that week. Therefore, plastic foil was taped over the window. At that time, I could only tilt the window and make a hole in the foil.
After the screed (about 12 days ago), I have been diligently ventilating at least twice a day for about 10 minutes each time. According to the hygrometer, the humidity is now about 55% on the ground floor and about 80% on the upper floor.

I think the mold was directly on the concrete (picture 3).

What do you think about it? Does something like this happen to you as well?
THANK YOU for your reply.

That is completely normal and harmless.

That is completely normal and is harmless.

Hello Mycraft,
thank you for your answer.
What should/must I do now about the mold?

As soon as the humidity returns to a normal level, it can be easily removed. On the concrete wall, it is not mold but the normal concrete efflorescence.

Did you also check the wooden beams?

have you also checked the wooden beams?

Which wooden beams do you mean?