u/AffectionatePin1060

I recently opened my concealed cistern after having had to remove discolorations from my toilet bowl on an almost daily basis for the last couple of months. This greeted me, but there seem to be no similar pictures anywhere and I just can't figure out, whether this is mold or anything unhealthy in general.
Anyone seen something like this before and able to tell me what this is? My landlord insists this pollution is normal, but I don't quite believe them yet, since I've had trouble breathing for a while and it disappeared, once I had removed these blobs...