So I was just doing an inspection and ran across this weird brown spot on my stem. It's not stem rot or anything as it's been super dry, so I'm thinking some type of stem borer? Usually those are round though. Something definitely went to town.
Exactly. If your plant is showing a certain deficiency mid-late flower, then giving them some ready to absorb nutrients isn't going to destroy your soil food web but it will give them the nutrients they need to finish flowering.
"Applications of synthetic fertilizers kill off most or all of the soil food web microbes."
This is outdated. As long as synthetic fertilizer is not used in excess, it doesn't harm the soil food web. There was a journal on this somewhere I'll see if I can find it
Happy Frog will have plenty of nutes for them until they reach the OF. I would suggest a slightly larger inset than a solo cup so early seedling roots don't reach the OF too fast.
This is a bit of generalization, there's nothing wrong with topping outdoors. I know plenty of growers who do both. Some strains respond better than others.