Stirred resin for 5 minutes then poured into another container and stirred for another 5 minutes.
Added a glasscast blue pigment and stirred for another couple of minutes to blend.
Done a 2mm pour and torched out bubbles but have observed this anomaly in a section of the pour.
Can someone tell me what’s going on here please?

I think it is rather a case of how you mixed and not for how long. make sure to scrape along the walls and the bottom of the container and use a suitable mixing pot without any plastic reinforcement fins in the bottom or anything like that...