It could be quack grass.

I don't know what it is but in my experience, broadleaf herbicides don't work that great on those. I would suggest something triclopyr based, like Weed B Gon Chickweed Clover and Oxalis or this stuff https://www.amazon.com/Brushtox-Brush-Killer-Triclopyr-32/dp/B01BOZ5VPI/ref=pd_lpo_86_tr_t_2?ie=UTF8&psc=1&refRID=BD9HT1FYTP5XM0NEN9AA

j4c11 - Thank you. I spent some time googling and found what seemed like an excellent article on controlling different weeds, as well as advice that a combination of treatments would be best. I was thinking of the following: Dicamba, Triclopyr and 2,4-D with MCPP/MCPA Linking to the article on Grounds Maintenance / treatments for different weeds here:

Looks like yellow nutsedge to me. If you pull one up and roll it in your fingers, do you feel 3 edges? Remember that sedges have 3 edges. They are neither a grass or a broadleaf weed. Nutsedge produces hundreds of thousands or millions of tiny tubers or "nutlets" as part of its rhizome network. The tubers are viable for years and can germinate at almost any time. They are controlled with herbicides like Halosulfuron methyl (Sedgehammer).