Japanese Andromeda (Pieris japonica) and some of their Azalea and Rhododendron kin are vulnerable to a pest called Lace Bug, which sucks plant sap much like aphids do. Their presence is usually given away awhile after they have begun feeding, with damage called stippling, which we see here. Soon, if they haven't already, they will resume feeding for this year, so about once or twice a week, start checking the undersides of the leaves for the insects or their deposits of tarlike specks. Insecticidal soap is one of the recommended control approaches, but you need to make sure sprays coat the leaf undersides as thoroughly as possible, and repeat treatments are likely going to be needed to knock-down multiple generations. Follow label directions on the product you choose to use. https://extension.umd.edu/resource/lace-bugs-trees-and-shrubs

If these plants are receiving more than a half-day sun - or full sun - they tend to be stressed enough to make them more of a target for Lace Bug. Pieris is a woodland plant and not very well-adapted to the brighter light and higher heat of sunnier garden locations. Given that it may be impractical to move them at this point due to how established they are, just be aware of their watering needs throughout summer and autumn to help minimize any stress. If they are getting shade during the hottest afternoon hours, then this may not be an issue.

Paler foliage can also indicate poor root health (with Pieris, often from poor drainage or overly-wet sites) or under-nourishment. Your use of Holly-tone is fine, as it is formulated for acid-loving plants, as Pieris is, though as an organic fertilizer, it can take time to show any measurable effects. (Organic and slow-release are good traits to have, but this is just another factor to be aware of.) Having a laboratory soil test done before applying any additional nutrients or soil acidifier would help in determining if any other intervention on that front is needed. Otherwise, twice-a-year fertilizing with Holly-tone is probably fine, though shrubs in general do not need as heavy a nutrient load as, say, annuals or vegetables. Once each in spring and fall should be sufficient for dosing times; otherwise once a year is also likely to be plenty. It's possible the soil only needs acidification going forward, as nutrients might be in ample supply but not readily accessible to plants if they aren't in the ideal pH range. The front porch concrete may be raising the pH over time, but only a test will determine if pH is an issue. https://extension.umd.edu/resource/soil-testing-and-soil-testing-labs

Twig or branch dieback tends to result from root loss due to soil over-saturation or compaction (which impedes drainage and oxygen levels for root health), or fungal infection of the stems themselves. If the latter, fungicide treatments tend not to be practical or effective, so just trim out what dieback you find and, as before, monitor the root zone for any watering needs. https://extension.umd.edu/resource/watering-trees-and-shrubs

Miri

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