All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
You should avoid these obsessive whispers and not give them any consideration as there is no better cure for whispers than totally ignoring them and not paying them any attention.
As regards these spots which you inquired about, they are not deemed impure; rather, by default they are pure if they are as you described. So you should deal with them normally and not consider them as an impurity.
You should not heed these whispers and not get carried away with them as getting carried away with them leads to much harm. For more benefit, please refer to Fataawa 83401and 199253.
Allaah Knows best.