Hello @tutina, I would like to add my welcome to Connect with @colleenyoung and other members. Here's some information that hopefully will help you understand the condition in layman's terms.

Benign fasciculation syndrome: What causes muscle fasciculations?
– https://www.medicalnewstoday.com/articles/320388

To repeat Colleen's questions, are your sons by chance taking the same medication, for example allergies? How long has your eldest son been taking the additional minerals and vitamins (D, B12 and magnesium)?