Most likely, the distortion and lines are due to cold damage to leaves that weren't yet completely developed. It won't go away, but it won't get worse either.

It is only happening on new leaves. Young leaves rolled and distorted could be either chemical damage or Rhododendron Gall Midge, Clinodiplosis rhododendri. Chemical damage should be associated with a chemical application (fertilizer, herbicide, deicing salt, etc.) and should affect more than one plant. The Rhododendron Gall Midge is a native pest of Rhododendron catawbiense, R. maximum and their many hybrids during the May to October growing season. The larval feeding damage from this fly can cause discoloration and distorted foliage. This damage can appear as in-rolled, twisted leaves that have turned a yellow color. This can be seen on young leaves that have separated from the bud scale. Leaves attacked in the bud stage may die if the injury is severe.

Care must be taken to distinguish this pest damage from similarly manifested damage caused by leafhopper injury, chemical injury, leaf-roller activity and aphid feeding. There is no way to undo the damage once it has occurred. Control is effected by applications of insecticides with the bud break stage of rhododendron development. An alternative would be to maintain healthy plants so that they could survive any damage caused by an infestation or to prune newly-infested foliage that contain larvae.

To keep them healthy, the most important thing is good drainage. The pots must have good drainage. Second, don't over-water. It is much better for them to wilt a little in the heat of the day than to be over-watered. Watering every day or two may be too often. I would cut back until you see a little wilting on new leaves in the heat of the day.

Here is a link that might be useful: How to care for rhododendrons

According to the info I could locate, damage from Rhododendron Gall Midge doesn't look anything like OP's images.

oops. I also meant to add that, yes, those are new leaves, but it took a while for them to get this large.

I still vote for cold damaging some cells of the much younger and not yet unfurled leaves. The damaged cells couldn't enlarge as they should have. And the leaves now appear as shown.

Thank you so much for your responses - much appreciated.

Here's a 48-hour update that may point to both of your comments (because maybe there is more than one issue going on): I went out this morning and saw one leaf cluster that seemed covered with white, at first glance. At closer inspection, it looks like pinprick-sized areas of the leaf have been eaten. On the leaf underside is a sooty, soft mold-like build-up and some tiny light green caterpillars(?) with black heads. I don't see any wings, and this is the first I've seen anything like this on the plants. I've posted close-up photos at the top of this page: http://docs.google.com/View?id=dfpvsgps_378q8vjwc6

This looks like a picture of a leaf-roller I found online. Could that be right?

Here is a link that might be useful: new photo of leaf damage

Yes, you have found the culprit and identified it.

To control, use Orthene, Malathion, or Diazinon.

Many thanks!

Lynn,

Those are the culprits of the "lace-leaf" damage. But not of the folds & "pinches" seen in the 1st 4 images you posted.

The line damage is caused by leaf miners, Caloptilia azaleella. This tiny caterpillar 'mines' through the leaf, and leaves a line wherever it goes. The leaf miner also skeletonizes the leaf. These caterpillars hatch as the new growth is forming, and may also roll the leaf with a white web. Damage only occurs on soft growth. To control, use Orthene.

Distorted leaves can also be caused by cold damage that occurs on leaves that start forming just before a cold snap, or leaves that come out too early in the spring and are caught by a cold snap. Such damage usually includes tissue damage which causes the brown, burned areas.