A: Happily, no.
The leaves of our evergreen shrubs are long-lasting, but not eternal. In a normal fall season, some leaves would yellow and drop or blow away from these plants. Normally, you’d not see enough of them to notice, or in the case of the magnolia, you would – and it’s just a bunch more than normal this year. Plants shed some of their most heat-stressed and less useful leaves as they make ready for winter, and they have more they’re shedding this year because of the severity of the summer heat and drought we just went through.
Mother Nature’s doing most of what you need, with cooler temperatures and rain. Just make sure that you feed your shrub beds once this fall, and again in the early spring. The flush of new growth next year should fill your plants in nicely, and by the time April or May roll around, you’d be hard pressed to see that anything had stressed your plants at all.
(I would recommend a sprinkler check in the spring, just to make sure your stress wasn’t also due in part to an irrigation system failure. But the heat alone was enough to give many plants a hard time this year!)