Adding nutes to the AG

So, I've got one plant growing in a first time AG grow. I've been advised to add some nitrogen to my plant to darken the leaves but I have no idea how to correctly add anything to the well and I really don't want to kill the plant.

Advice?

Thanks!

All the more reason for a trip to your local hydroponics store to see what's on the market. I've been happily using Technaflora's "Recipe for success," and it's done well for me but I know there are other brands on the market. Try for one that has a sample kit that will let you ease into it without spending a fortune and discovering that you don't like it.