Nutrient staining is a thing with some product lines. Nothing to freak out over if the plants are healthy.

Seeds are lottery tickets. It’s possible to win the lottery. Odds are not in your favor. Connoisseurs are willing to sort through the trash. When and if a grower finds something truly worth keeping from seed. The ability to clone is priceless.

I wrote this 10 years ago but the info is still solid.

The Fundamentals of Cloning