First of all, the yard looks pretty danged good.*
Regarding pictures 1 and 3, it often happens that when two massive concrete structures come together like that, the heat retained by the concrete will dry out the soil much more quickly than the rest of the lawn causing the grass to suffer from drying out. Those spots need to be watered more deeply.
As for picture 2, when it rains, does rain and/or roof water drain through that area? I have a picture...
The dead zoysia in front of the beds is in a low spot where all the water from his yard drains. I don't know what variety of zoysia he has, but this dead spot only happens after prolonged rainy periods. His grass had a chance to come in before the rains hit, so it looks a little different.
* Side notes:
Never use an insecticide just in case. Always verify that you have the problem before spraying. Grubs are normally only a problem in late July and August, but even then you should dig up a square foot of turf and search for grubs. If you find fewer than a dozen, then restore the dirt and sod without spraying. If you find an uncountable mass of grubs, then go ahead and do what you have to do. One more thing about insects and pictures 1 and 3, chinch bugs love hot soil especially in the concrete corners like that. If it were later in the season I would suspect chinch bugs, but you said the grass never came in. You can check for chinch bugs by wiping your hand across the grass (back where there is grass). The cinch bugs normally hang onto the grass blades, so when you wipe your hand across, they flick off into the air. You can use a piece of paper for them to land on. If you get them landing on the paper, then that is your issue, but again, I think it is too early for them. Check anyway.
Your tree in the middle of the yard has too much mulch at the base. The roots should be exposed at the very surface as in this picture.
They don't need this exact amount of exposure, but the important thing is that all the bark on the trunk of the tree has access to fresh air. When it is mulch up like that the trunk bark will get a fungal disease which eventually makes the tree look ugly before it dies completely. I realize that you see trees mulched like that in every community, but that doesn't make it the best practice. If you like the built up look of the mulch, you can create a crater in the middle which exposes the trunk down to the roots.
