Not sure how you landed in this forum - Weeds would have been a better choice :-))

Your weed looks to be crabgrass. The Weed B Gon won't have any effect on it as that addresses only broadleaf weeds, not grass-like weeds. It is an annual weed and can pop up any time during the growing season but most frequently in spring. To treat now, you either dig it out or use a herbicide that is registered for crabgrass. Weed B Gon actually makes one that includes a crabgrass control but cannot be used on all lawn types. And you will also need to use a pre-emergent in spring to avoid the spring seeding.

If you repost in the Lawn Care forum, they will confirm ID and provide you with various recommendations on both how to remove and how to prevent.

Oops! Definitely not the forum I meant to post in, but also didn't see the weeds forum...didn't scroll down that far. Thanks for the heads up and thanks for the input!