What are the marks, post heat treat?

[WNC Goater]

Another newb question. Can anyone tell me what these small circles are? Not there prior to heat treating but there after sanding away the firescale. Small circles are approximately 1mm across. First two blades were of 1095 and each had 1-3 of these marks. Blade #3 in 1095 was clear. Last two blades were of 1084 and each had a couple of these marks. After the first two, I cleaned them with alcohol before heat treating to wipe off and remove any residual oil, thinking perhaps some speck of something was on there. Last two (1084)were carefully cleaned, laid on a paper towel while the oven heated and not touched on the blade area at all until after tempering.
So initially I thought some dust or something was on the blade but after carefully cleaning the last two I'm wondering if it is some impurity in the steel??

First blade, 1095 (scratches from using and testing)



1084 blade


1084 blade with large mark and "halo" circle