stains/dots on viewfinder

Hi all,

yesterday I noticed that when watching through the VF there is black spot almost the size of the AF points and a smaller one.

I checked and verified is not on the lens and also not the external VF, seems to be inside.

I have tried to blow the mirror and the sensor with air but no luck.

guessing is on the mirror or on the screen where the mirror goes when it locks up or in the pentaprism?

suggestions, advices?