Call the manufacturer and tell them you applied a chemical without knowing what you were applying and ask them what to do. You are lucky this chemical only kills broadleaf weeds. If you had applied an all purpose plant killer you might never be able to plant anything in your lawn area for several years.

Spectracide Weed Stop is a common broadleaf plant killer containing 2,4,D, Dicambra, and something else that does not come to mind right off. While it is not a really good product to use and while it can also kill plants you want to keep if due care in use is not observed, it is not quite as bad as some others mainly becasue the formulation is not really very strong. It is not quite as bad as maifleur makes the stuff out to be, and the manufacturer will simply tell you there is no problem.
The most bestest way to control "weeds" in your lawn is to get that lawn into a good, healthy condition and that starts with a good, reliable soil test. Contact your counties office of your Colorado State University Cooperative Extension Service about having that done and also dig in with these simple soil tests,
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2. Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
which can guide you toward a good, healthy soil that will grow a good, healthy lawn that will crowd out "weed" growth so you don't need those poisons.

Here is a link that might be useful: CSU CES

OK, no sermon, but you should still call the company to see if any residue remains in the dead plants. If there is, and I don't think 2,4,D disappears you will need to remove dead plants. If there is no residue you are good to go. However, next time ask questions like this before you purchase a chemical to use around your home.

Maifleur,
You are right, I should have looked it up first. I think I will just pull them all anyway, and that makes me think I should have just pulled them in the first place. It's just so much lawn (half acre)--it seems impossible and I'd rather be doing pretty much anything else.

Thanks

Jenzebel,
You don't have to pull the weeds, that's the beauty of that spray. In a week or two get some grass seed and spread it around to fill in were the weeds are dieing. Put more seed were you have bigger weeds like dandelions or other larger weeds. Then feed that lawn and it will look like a million bucks. Good Luck...
md

Awesome! Thanks mjmarco! That's what I was hoping for. I am going to wait 3 weeks, just to make sure. I'm so excited about having actual grass this year!

thanks for asking this question. it helped me as well.

"If you had applied an all purpose plant killer you might never be able to plant anything in your lawn area for several years."

Completely inaccurate statement!! Virtually all broadleaf lawn weed killers and even the broad spectrum herbicides like RoundUp deteriorate and become inactive rapidly after application. Typically you can reseed a lawn after 7 days and other plants can be planted in just a couple of days.

Since the dead foliage of larger weeds like dandelions or plantain can prevent grass seed from proper contact with the soil and so have proper germination, Id remove them as much as possible before seeding or overseeding.