Hmmm. Sounds like you made a major investment in your landscape. I'm not an expert, however, I do have a mix of drought-tolerant plants, natives, and traditional plants, but I only hand water once a week, and the natives only once every 2 weeks. Usually, I try not to water unless it's a new plant, or I see something wilting. Plants, in general, seem to be a lot more drought tolerant than we think. But it might also be the frequent shallow waterings. I might try longer, deeper soaks less often. It could be your soil. I recently went to Las Pilitas and they have some very strict recommendations about planting natives. They tell you to do a deep soak when you first plant them (which is very important) and then once a week or so (depending on the plant) for the first few months (sometimes up to a year) and then back off. I recently planted 3 drought-tolerant plants in the same general area, did my deep soak...and a three weeks later, 2 are going gangbusters, and one is shriveled up and brown. The only thing I can figure is there's something in the soil that killed it.

I would check the soil in the root zone depth of the new plants. I agree that 10 minutes sounds like far too short a time to water, and two days seems too frequent. Check to make sure the soil is at least a little moist a foot or two deep around the plants. For the first year I'd make sure the plants have moderate to ample moisture in the soil all summer. After that, they should be established well enough to need only perhaps a monthly very deep, thorough watering. One possible problem with the plants is that the planting hole is probably softened soil in what may be hard, relatively impermeable soil, so all your water is saturating the planting hole. In effect, your plants may be sitting in a hole full of water. On the other hand, they might be getting too little water. Before you change what you are doing, dig around a little and see how wet the soil is. Moist soil is good, mud or dusty conditions are bad. If moisture seems OK, maybe it is just bad luck. I'd would expect to lose a plant or two, but you shouldn't lose more than 10 or 20% even with really bad luck.

The fungus gnat females lay eggs in the potting medium; the tiny larvae are wriggley maggots. They feed on the bits of peat moss and other particles in the potting medium as well as the tender root tips of the plants. The key to preventing these troubling larvae is to carefully manage the moisture content of the medium. It is never appropriate to allow a plant to become dry to the point of wilting, or to water in tiny sips. Container plants need to be drenched on watering day.....then allowed to dry out appropriately. It's imperative that we use a porous, coarse textured potting mix that welcomes drenching, yet drains rapidly. A peaty, dense medium invites fungus gnat activity.

Brown tips may be from salt buildup in the soil or from something that was sprayed on them. If the former, flush with copious amounts of water. If the latter, rinse with water (although it may be too late). The soil looks like it has a lot of peat moss which will cause excessive water retention and root rot. (I know you checked for root rot but it perhaps you did not see it.)