I've started to paint my basement with white primer, and on one wall weird orange spots appeared in the holes I had "filled" with the primer.
The wall is made of dark cinder blocks which are pretty rough. I have to use a lot of primer in general with the roller and need to touch up with a paintbrush all the major holes to fill them.
At some point during painting I noticed the yellowing in one hole, but didn't think much of it and filled it again.
After 3-4 hours I checked on the wall again and saw 2 dozens such spots in a bright orange color, much like rust. One other wall isn't affected at all, but the primer I used was a different brand. Now I'm using a new KILZ 2. Before, I was finishing a Benjamin Moore white satin paint.
As you can see from the picture the hole is still "closed" by the paint.
In that section the wall is pretty dry. We've had some efflorescence near the ground (which I've removed), but not at all where I'm painting now. The wall is 25% above ground and the spots have appeared both above and underground.
The wall was also painted with just one layer 8 years ago on one section of the same wall before we bought the house, and I've now noticed the same spots.
Any idea what that could be? I'll be continuing with the painting over the next days.
Here's a picture of the unpainted cinder blocks.