white balance - Color temperature changing with altitude?

After 50+ years of traditional photography, I went 6 months ago for drone video&photography. Incredible what the change in perspective can do... Anyway, the question is now related with a dominant tint I'm getting when I shoot at very high altitudes. I just shot 5.5 hours of videoclips & photos in the high lands of Argentina and Bolivia, between 3,800 and 5,500 meters above sea level. When I watched them, back home, on a serious 4K computer screen, I realized that they were terribly tinted in brown/magenta and now I'm struggling in post-production to color-correct them. I used the Auto White Balance setting for all the takes, and it seems that the higher I went the more brown/magenta the videos are hued. Any idea to avoid the same problem in future? (Yes, the good old "adjust the white balance every time you shoot pointing at a white piece of paper" would also do...). Thanks, folks.