What is this growing in my lawn?

Hey all – moved into a new house a few months ago. Can you help in identifying this small weed? It has started growing over my ENTIRE yard in the last 1-2 weeks at the same time. Is it clover, and/or any idea how it can spread that fast? Only treatments I’ve applied are 2,4-D and a generic insect killer a few weeks ago.

Thank you!