I am located just North of Tallahassee and my St. Augustine looks exactly like yours! I was told mine is fungal disease.

Well seeing the tips of your grass you need to sharpen your mower blades And what normal comes with unsharp blades is an infection

Thanks for the feedback guys. Any recommendations for a good fungicide to use on it?

Can you retake those pictures on a cloudy day or in the morning before the sun hits it (no flash)?

You are watering too frequently. You should be watering more like once every week or two (YES, once every 7 to 14 days). But you should be deep watering when you do. Here's more...

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

Second, you should be mowing at the mower's highest setting every 7 to 14 days. YES, every week or two. Tall St Augustine will grow much deeper, more drought resistant, roots.

I have been very successful getting rid of fungal disease in St Augustine using ordinary corn meal at a rate of 20 pounds per 1,000 square feet. Apply to the entire yard because it will create green spots if you only put it on the fungus spots.

Thanks! Some great info there. So ordinary corn meal has worked out for you? What is it about the corn meal that fends off the fungus?

Corn meal gets decomposed by bacteria and fungi living in the soil. One (or more) of those fungi are particularly attractive to another soil fungus which is predatory to the others. When that happens, there is a population boom of the prey and the predator. When the predator is finished with the fungi on the corn meal, it goes to work on other fungi like the one causing the disease. If you go looking for more information on this, you will circle around to me and a few others who have had success. You will also find a couple of naysayers (Dr Chalker-Scott and Dr Parsons) who have never tried it, but they just believe it doesn't work. It has worked for me every year since 2002. It was the only thing that got my St Augustine lawn back to health the first time, so I've stuck with it.

Ahhh I see. So if I applied corn meal using a broadcast spreader, what ballpark setting would be a good start to get close to 20lbs x 1k? Also, should the CM be applied before a rain, or after?

Here are a couple more pics of the troubled areas under lower light.

I use a Scotts spreader at the max setting for corn meal and soybean meal. I do multiple passed in perpendicular directions and it works well. Make sure you don't' do it on a windy day because of all the dust.

With my spreader I had to go over it 4 times with it wide open to get 20 pounds per 1,000. Now I throw it by hand. I use a 2-pound coffee can and spread that over 100 square feet (10x10 feet). Then I move on to the next 100 square feet.