I would make the sprinkler water very early in the morning, say around 5am so the moisture evaporates quickly and does not stay in the shrub long enough to start fungal infections. I would also increase the amount of water and make sure there is plenty of mulch so the waterings last longer. Lack of soil moisture triggers browning from the tips inwards in the summer months. If you water by hand, water the soil and not the leaves.

That's all taken care of. Sprinkler waters at 5, it doesn't hit the top of the plant, it's well-mulched and watered 3X per week plus extra on days we near 100.

I'm trying to figure out if it's a fungus, and if so, what kind.

Not usually. When it starts in the summer months, it is the dry weather causing the problem unless one is overwatering or getting leaves wet for long periods. Fungal infections will require the often presence of moisture and that is just what many of us are looking from the skies! Hee hee hee! btw, the leaves will not recover of course but the problem should stop. If unsure of when to water, insert a finger into the soil to a depth of 4" and water if it feels dry or almost dry. Do not count the mulch on those 4" by the way.