Heya
Interesting stuff..
I've been doin this kind of thing for years, and I've noticed one particular truth, and that is, powders can be from somewhat, to extremely sensitive to ambient temperatures depending on the specific powder used. Each particular powder reacts to changes in ambient temps in a different way. They are not the same across the board.

If I'm understanding your data correctly, you had a 10°F difference between sessions.. This could account for some variation in your velocity results.
In my experience, once you start shooting in ambient temps above 90°F, chamber pressures start climbing and so does the ballistics(including velocity results) of any particular load.

To confirm this, reshoot the "same test" in as close to the same ambient temperature and conditions as possible and see if your results are more consistent.

Also I've never found a huge difference in standard small pistol primers as far as ballistics each brand will produce.

Cleaning or not cleaning would not account for any of this either..

IF this doesn't answer some questions, then there is "..somethin happenin here...