What do see that you think is affecting the plants? All I can detect is some small brown areas; certainly too little to be spraying.

It looks nearly identical to peach leaf curl, hence the guess that it is fungal.

Leaf curl can occur due to insecticide use or extreme cold & lack of soil moisture at the time (which results in desiccation); water deeply before very cold events if the soil has not frozen. Azalea leafminers also cause curling and they hide inside the curled leaf. An aphid infestation in Spring can also distort leaves and cause curling; the sucking of these insects can leave lesions in the leaves that turn colors based on oportunistic fungal infections. A very large infestation eventually covers the leaves with dark excrement, a honeydew like substance that attracts ants.

Peach leaf curl is entirely species related. Leaf contortions on other plants, especially in spring and especially with new growth, are typically due to aphids, so not fungal in nature. But as noted, other insects can cause similar symptoms.

Update on this. New growth continues to exhibit gnarled curling. Have sprayed every 7 days with neem oil, with no apparent improvement. No aphids or other insects visible. I will be attending a sale on mother's day where I expect the original grower to be present, and I will inquire if they can identify the issue. The plant came from White's Nursery in Maryland. They specialize in Rhododendrons and azaleas.

Cheers,

Werner