Yup, malt has a ton of nutrients, unlike wine must, apple juice, or honey, so nutrients aren't necessary. When you're stressing the yeast, you may want to add some just for caution. I have two pounds of bakers yeast that makes terrible bread, so I toss a tablespoon into all my high gravity brews during the boil. Yeast love to eat yeast bits.
The only time to ever add nutrients (to beer- wine and mead are different stories) is during the boil to sanitize it. You're perfectly fine.
I can't be arsed to keep up this list of what's in the fermenters, but hey, check out the cool brewery I'm opening up!
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