Annual bluegrass, "Poa annua" will do that and many sellers of grass seed include this "weed" in their mixes for some unknown reason.
What is your soils pH?
What is the level of organic matter in your soil?
What is the nutrient level and is it balanced?
What kind of life is in your soil?
How well does your soil drain?
Contact the local office of your University of Georgia Cooperative Extension Service about having a good, reliable soil test done and then dig into yor soil 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.

All of this will help you make your soil into that good, healthy soil that will grow a strong and healthy turf that will crowd out the "Poa annua"., but it will take some time and probably more then a year.

Here is a link that might be useful: UG CES

Unfortunately if you've been on TruGreen, your soil is probably in pretty bad shape. You need to do more to stimulate the life in the soil then just apply some organic fertilizer.

1. Apply a HEALTHY dose of compost. And make sure its GOOD compost. It should cost $5 a bag and should be dark and fine. It should not look like mulch.

2. Apply some DRY molasses if you can find it. Sugar will help stimulate the biological life in your soil. It will not attract ants, but will actually repel them.

3. If you can make some compost tea, do it and spray it onto the yard in the cool part of the day. These will feed your soil beneficial microbes. Of course, make sure you dont spray it in with chlorinated water, or you will kill off the organisms and waste your time.

4. Chlorine in water can be a problem for trying to go organic. You can buy a chlorine filter to attach to your hose. Costs about $50 and lasts 6 months. If you dont want to go that route, make sure when you water you get a sprinkler that sprays and do it in mid-morning. The spraying effect and a little heat of the day will help the chlorine to evaporate.

5. ALWAYS leave the clippings on the lawn. Provides nitrgoen and organic matter.

6. DIVERSIFY your organic fertilizers. Use Alfalfa one time, Soybean another, Cottonseed Meal another time. The more diversity the better.

7. DONT GIVE UP!!!!

you haven't waited long enough

last spring i put down compost purchased from a local organic nursery. over the summer i added rabbit food or dry molasses once a month or so just before a good rain was forecast.

last fall i put topsoil in the low spots, over-seeded with 3 different types of fescue put a good layer of leaf compost (purchased from a local bulk mulch company i trust) and added more alfalfa pellets once things started growing.

i didn't add that i've got a small yard and two very big dogs.

this spring the grass is amazingly green, lush, thick and looks much better than the neighbors

i didn't measure anything, and didn't do any soil test. I figured that given enough time things will correct themselves.

give your lawn some more time & think of it as more of something you've got to build than apply.