The first ones are very like amaranth, whose seeds are also everywhere in my region. Don't despair. amaranth leaves are not only edible they are very nutritios. If you don't like them out of hand, they can be sauteed and make a fine fritatta.
And I concur on the square stems. Peppermint and monarda, both being members of the mint family should, will have square stems. I don't know how soon they develop their distinctive smells. It takes a while from seed to have
enough energy to make oils, and the function of the volatile oils is to cool the plant, thus in nurturing environments of perfect temp and humidity we tend to provide for seeds and seedlings, the fragrance may not be there right away.