I was watering 2 times a day, 18 minutes starting at 6:45am, then 10 minutes at about 4pm, since the weather gets to be about 90F then. I'm not sure how many inches that translates into. I've since cut down to only 18 minutes every morning at 6:45am now. The top of the soil seems pretty dry after i get off work every day if I don't give it some water in the afternoon, so I'm really scared of only watering it like once every 3 days or longer as recommended. This is my first time owning a house and a yard, so I'm probably overwatering like crazy.

If I understand correctly the grass looked fine for several weeks and suddenly got the various symptoms you described. Is that correct? You severely over watered for the first month and that is what led to the symptoms. The installer should have told you to water 3x per day for 10 minutes each time for the first 3-4 weeks or until the sod roots knit into to the underlying soil. Then start backing off on watering until you are watering every 5-7 days for about an hour. Even your nutgrass problem could be caused by the overwatering. It is a swamp grass and thrives with too much water. All the symptoms sound like fungal disease. The blob that looked like dog barf is commonly called dog barf fungus. It happens to be very ugly but it also happens to be harmless. You probably cannot really tell where that spot was several weeks later. The white stuff was likely powdery mildew. The blue areas were symptoms of not enough water but there are fungal diseases which cause the same symptom. The strong temptation is to add more water when that happens, but that is the wrong response. All the water goes to the fungus. How high/low are you mowing it? The installer should have also told you to mow at 4 inches (mower's highest setting). But this time of year is when you should be skipping mowing and letting the grass get up to 5 or 6 inches to endure the summer heat. Scalping fescue this time of year could be the problem for the large area that is dying. If you are mowing at less than 3 inches, then you cannot blame the installer for much of any of this.

You should have been keeping the sod moist by watering it LIGHTLY, three times per day, for the first 3 weeks after putting the sod down. It doesn't sound like you were doing that. Regardless, it sounds like it's wet enough now. Zoysia has a fatal flaw in my book. When it goes bad, it doesn't seem to matter what month it went bad, it remains dead looking for the remainder of the season. Then in April (or March for you in FL), it finally comes back like nothing ever happened. So whether your problem was too much water or not enough water, the grass is likely to be "dormant" for the rest of the year. Can you lift any of the squares of sod or are they all knitted down to the soil by new roots? Did you get watering instructions from the sod installer? If so, what were they? Have you measured the output of your sprinklers? You can do that by timing how long it takes your sprinklers to fill several cat food or tuna cans placed around the yard. My sprinkler takes 8 hours to fill the cans. My neighbor's high flow system takes 20 minutes. It all depends on YOUR system. Once you have that time, that will become the time you water every time you need to water. It might seem like a long time to water but you're not going to do it very often. For example I did not water my Texas desert lawn until mid July this year. Why? Because the roots on my lawn were deep enough to capture deeeeeeep water from the occasional rain we got. But my yard might have been an exception for other reasons. Here's the basic watering plan for the US (except for the triangle from Green River, UT down to Palm Springs, CA over to Junction, TX). Water deeply and infrequently. Deeply means a full inch at a time. Infrequently means with temps in the 90s or above, once per week. With temps in the 80s, once every 2 weeks. With temps in the 70s, once every 3 weeks. What this does is develop very deep roots which can take advantage of every rain storm for a good long time. It also allows the soil to dry out completely at the surface which prevents new weed seeds from sprouting. Proper watering is quite often the last correction people need to make to get their lawn to the next level of perfection and stop using herbicides to kill weeds. Why did you pick zoysia instead of the more normal bermuda or St Augustine?

Does your lawn ever go dormant or turn brown in the winter? If it always stays green all winter, then that grass is dead and needs to be reseeded or patched with living sod.