Can I Add Mykos AFTER plants are growing?

I was reading about mykos and a friend gave me the rest of his bag. Apparently they are good for nutrient absorption

Can I add them to the soil even tho my plants are a few weeks old?

sprinkle it on the medium then add water or add it in the water but make sure you water right away. I think the beneficial Bactria will die if its not in the medium

Use the mycos when you transplant. It's most effective in the root zone.

Read up on a simple AACT bio tea! Keep your powders till you can mix it into the soil for the next run!
Gotta ask - synthetic nutrients?