I grew an auto in FF OF and didn't feed until 1month into it, still got a bit of a nitro tox.
It's a hot soil. There's nothing wrong with it, but maybe not optimal for all autoflowers. As long as you see no issues, it's a non-factor for you.
I did not have a good experience with FF nutes. It didn't provide what the plant needed and i needed more supplelents, plus that liquid junk is expensive regardless of the brand. Avoid all products with cartoon graphics on the label, lol! "pot" brands are the worst and most expensive, typically.