The move to lower the age for blood donors began around 2015:
https://www.usatoday.com/story/news/health/2017/09/24/loyal-blood-donors-age-industry-out-young-blood/683714001/
Around the same time teen blood began to be “ enriched” as the industry encouraged young donors to raise their iron levels:
http://aabb.org/advocacy/government/fdaliaison/bloodcomponents/Pages/flm170131.aspx
The Red Cross began to screen for ferritin levels among teen donors in January of 2018. This is not public knowledge.