More pictures of the yard as a whole. Some areas look great and are a deep green.

This is the section that looks great.

Your instinct about the disease was correct. Now that it's too late, go back and reread the directions on your fungicide to see if you can apply with temps above 90 degrees. Most are only good up to the low 80s. I'd hate to see more damage come to that lawn.

There is a natural method of disease control that works well for my St Augustine. Corn meal attracts a fungus called Trichoderma. Trichoderma is a predatory fungus that feeds on the disease fungi. It takes 3 weeks to see improvement but I've been using it every year since 2002 with good results.

I water 3 times a week at 35mins per station due to it being 100 degrees and no rain in sight here in East Texas.

That's weird because with our drought restrictions during 2014 we were only allowed to water once every 2 weeks and we made it just fine. My preference would have been to water once a week, but the water police were enforcing the restrictions. The reason you got the disease was too much water. If you had been watering during the rain events of 2015 you might have set this up. The watering schedule that works all over is called deep and infrequent watering. Deep means 1 inch all at one time. My sprinkler can only put out 1/16 inch in 35 minutes. You'll have to measure your own because everyone's is different. Put out some cat food or tuna cans and time how long it takes to fill the cans. That's your new time for watering. Note that every zone might be different, so you'll have to measure every zone. Infrequent means no more than once a month with temps below 70 degrees. With temps in the 70s water once every 3 weeks. When the temps get into the 80s go to once every 2 weeks. In the 90s go to once per week. With temps above 100 you can go to once every 5 days.

Mowing height makes a big difference. It appears you're okay and mowing at the mower's highest setting. Perfect. At my last house I let the St Aug grow up as high as it wanted. It stops at about 32 inches high, but I had one spot in the shade of the house and an oak tree where I had stopped watering in October of 2011 and sold the house last summer without ever watering that spot. It survived from rainstorm to rainstorm during a 3-year drought. So I'm not feeling your pain about the 100 degree heat and no rain in sight. This watering plan came to me via Phoenix. East Texas is positively soggy compared to Phoenix.

I appreciate the response. I am going to cut back to watering once a week. I did not water at all during all of the rain that was going on 2+ months ago. I'm at the second from highest setting on my mower but I'm going to go ahead and set it to the highest setting again like I was doing 3 months ago.

I read the fungicide directions and bag very well and more than once and did not see anything about applying in a given temperature.

OK here is an update. I have applied bayer fungs control for lawns at the curative rate to the front and backyard. There are more deadspots in the yard right now. I applied the fungus control 2 days ago so it has not really had time to do its work. However I noticed the grass is very fragile in the dead spots and in the green spots this is what the roots look like(see pic below) Is something else going on? I have switched to just watering once a week for an inch of water this week.

About all you can do now is wait a few weeks to see if the Bayer works for you. Assuming it does and the grass shows improvement in a few weeks, I would suggest you apply some compost (no more than 1 cubic yard per 1,000 square feet) or compost leachate (plunge a handful of compost into a 5-gallon bucket of water a few times, pour the water on the lawn and put the compost back into your compost bin or bag. Why? Because the class of microbes in your soil that seems to do the most good is the fungus. Everything is interrelated among fungi, bacteria, protozoa, and microarthropods, but the biggest population is fungus and you just sprayed a fungicide. By waiting several weeks for the fungicide to dissipate and then inoculating the soil with the beneficial fungi from the compost, you will go a long way to restoring normal biology to your soil. It would also help to feed an organic fertilizer about that time.

Also I'm curious as to why my grass that is in shaded areas is still super healthy and green? Any ideas?