I have a fescue lawn that is about 1.5 acres (hand picking weeds is not an option). As spring began, these weeds (see pictures below) have started growing in the fescue. My guess is that the tall thin bamboo looking weeds are crabgrass? No idea what the rounded leaf weeds are. Any advice on how to get rid of them?
The tall grass weeds are not crabgrass, as that grows horizontally, not vertically. It looks like it could be quackgrass instead. The round-leaved plants are violets.
There is not one herbicide that will kill both weeds and, in my experience, no herbicide will kill mature violets in one application. Over the years I've spot-treated violets with broadleaf killers like Weed-B-Gone and the best control I could get was killing the top-growth of adult violets and outright kill of seedling violets. The adult violets always regrew from their stems. I have seen websites that promote one or more herbicides to kill violets, but they're always promoting the herbicides that they mention. They usually almost always mention Weed-B-Gone, which I know is ineffective, so I lack confidence in any of their other recommendations. You might have success against violets by spraying them throughout the growing season each time the stem regenerates new leaves, effectively starving or exhausting the plants so that they finally die.
The grass is a worse problem, because herbicides that kill a weed grass will also kill all other grasses. If the weed is quackgrass, then you're also pretty much out of luck, as even RoundUp isn't completely effective on that grass (it regenerates from its rhizomes unless you can spray every one of the grass's blades).
I hand-weed my violets and mow/ignore any quackgrass. I'd probably be better off if I just enjoyed the violets' flowers and ignored them, too.