I have Floratam - mid Florida. My initial Spring shot at the weeds is with Scotts Bonus S. - my first appplication of fertilizer. Later I use "Image for St. Augustine Grass and Centipedegrass with Atrazine." It requires several days for the weeds to go away but it has been pretty effective. Some weeds like Dollarweed do not completely go away but the Image helps to control it. Big box stores such as Home Depot have it. You should read the label - open up the sticky thing on the back to get to see all of it.

They don't exactly work that way :-) Your choices are a broad spectrum weed killer (like glyphosate) that can kill anything; a targeted herbicide for broadleafed weeds (which would include the clover) or one that targets just monocots or grass-like plants. Herbicides can not differentiate between a desired plant and a weedy plant - YOU have to do that. The best suggestion would be to use a hand-held liquid lawn weed killer (like Bayer Advanced All in One Lawn Weed Killer) but only apply to the species you wish to remove. Or remove them manually

Where do you live? What kind of seed did you put down? Did you use a starter fertilizer? What is your watering program - how often and for how long? Lawn care is as easy as watering, mowing, and fertilizer. You're already overthinking it. This is the right time of year to seed a northern grass to minimize weed issues. Had you come here before seeding we would have suggested you water the bare soil daily to sprout any new weeds and then spray those out with RoundUp. Then you could seed without fear of getting weeds. But here we are. If you have broadleaf weeds in the old lawn, spot spray with Weed-B-Gone. If you have chickweed, clover, or oxalis, you'll need Weed-B-Gone Chickweed, Clover, and Oxalis killer. It's a different, stronger, product. It will not harm the old grass, but read the label for instruction around new grass. Forget about weed n feed products. They usually don't do what you expect them to do. The problem is when you need weed killer you don't need fertilizer and vice versa. If you want to fertilize now I would use an organic. You can use that at any time even on the day you fertilize with a chemical fertilizer. They do different things for the soil and plants. You can use the organic over the new and old lawn at the same time and at the same rate. Start with 10 pounds per 1,000 square feet. In 3 weeks you can reapply at the normal rate of 15-20 pounds per 1,000. But you do need to spot spray the weeds in the old lawn. Then around Thanksgiving or so you can fertilize with a high N fertilizer for the winter.

What has the temperature been like there in Atlanta lately? I'm going to go out on a limb here, and guess "pretty dang hot"! Lawns under heat stress, drought, or high temperature conditions should not have herbicides applied. Usually most herbicide labels mention 90° F, what we call "weeds" are usually VERY hardy compared with turfgrass, have deep taproots and/or waxy coatings on the leaves. Consequently while the weed plant defenses are at their best in tough growing conditions for turf, the grass plant may be damaged. When it's real hot and dry there isn't much of anything to be done for a lawn, at least cool season turfgrasses.