No way setting 5.5 is putting down 28lb/k. I have the same spreader (edgeguard mini) and use setting 6 to get 4lb per k of Heritage G. I'm not even sure if the spreader was completely open you would get 28lb/k. Something is off.
So you put a whole 30lb bag on just over 1000sqft?

Even if you applied correctly, which I suspect you did, you should follow up with compost in a few weeks. The fungicide will kill thousands of beneficial species of fungus in your soil. Compost replenishes them.

jdo053103, it put down practically the entire 30 pound bag.

I checked the spreader window before I put the fungicide in to make sure it was opening and closing properly, and that it wasn't stuck open all the way (which can happen if a spreader wasn't cleaned after the last use, and sat for months). I also checked it afterwards.

Whatever happened, that's not my problem now. Right now I'm trying to figure out what to do. I've been putting down a lot of water, but I don't know if that will do it. The woman I spoke with at the manufacturer thought the grass might turn yellow, but couldn't say for sure.

I'll remember the compost, too. First I have to get past this hurdle, then finish putting fungicide on the rest of the lawn--at the right setting.

The damage from an over application of fungicide is to the soil microbes where the plant roots are. When the beneficial microbes are killed off, the plants growing there suffer. Those microbes are responsible for the nutrients your grass gets. You can also look for the soil to become extremely hard, not compacted, but hard.

The soil can recover but not until all the fungicide is decomposed. Because of the negative effect on the soil, fungicide is one of the worst things you can apply to turf. It should be used with the most care.

If this is St Augustine grass, there is an organic alternative which has worked for me every year since 2002. It seems to work for other types of grass, too, but it definitely works for me on the typical springtime diseases. The product is ordinary corn meal - yes the same stuff you cook with, only I get it at a feed store in 50-pound bags for the size and coverage I need. It cannot hurt your soil or grass...unless you completely smother the grass in it. The normal application rate is 20 pounds per 1,000 square feet. If you double that rate, no problem. If you quadruple that rate, you will know because you won't see grass anymore. Apply it, wet it, and let it work.

Corn meal works through a biological process. First come the fungus species which decompose the corn meal. Then comes a predatory fungus called Trichoderma (try koh DER mah). The trichoderma wipes out the fungus growing on the corn meal and then looks for other fungi growing on the surface of the soil. The fungal disease is right there and becomes the next meal for the trichoderma. This process takes about 3 full weeks to see results.

Corn meal is also a passable organic fertilizer. What this means is that if you only apply to the spots obviously affected by the fungus, those will turn dark green. To avoid having dark green spots in your yard, you should apply the corn meal to the entire lawn at the same rate.

Corn meal will not work if you have already applied a chemical fungicide because the fungicide kills off the naturally occurring Trichoderma.

Corn meal works on the most popular lawn diseases with the exception of any diseases characterized by red colors. So red thread and rust seem to not be affected by corn.

At your feed store don't become confused by corn meal and corn GLUTEN meal. That is a different product and will have no effect on the disease in your yard. It is also much more expensive.