Yea I don't think a seed can carry a disease...

This is the only thing that looks similar to what you had...

The most common reason growers will see a zinc deficiency is when the pH at the roots is too high. Zinc tends to get locked at higher pH levels and is better absorbed by the plant in a more acidic root environment.

The truth is, most cannabis growers don’t need to add more zinc in response to a zinc deficiency!

In fact, most growers have actually already given plenty of zinc to their cannabis plants since it is found abundantly in most tap water. If you’re using quality soil or cannabis-friendly nutrients, you probably don’t need to worry about adding more zinc. In general, zinc deficiencies are more likely to appear when a grower is using heavily filtered or reverse osmosis (RO) water to feed plants since any zinc has been removed, but pH is a much more common reason growers see zinc deficiencies in their cannabis plants.

I got this off of GWE...