Running short of water. To verify, stick your finger into the original rootball, then water as needed.

Oh yes, and check the other one also.

Thank you. I will increase watering, though I feel like I already water them a good amount. Is it possible the roots are not taking?

Yes, if the rootball got dry, the only way to get it to accept water is to dig it up and soak it in water for probably half an hour. Once dug up you can tell if it is accepting water by its weight. A light root ball is definitely too dry.

There are some other possibilities but I doubt they would appear so quickly:

Leaf spots have several origins:

Brown, reddish-brown or purplish leaf spots that occur on many cultivars, including R. 'Blue Ensign' and R. 'Mrs. G. W. Leak', are physiological and not disease caused. These spots are generally purplish and are inherent in the cultivar. Environmental stress may increase their appearance. They do no harm to the plant.

Some leaf spots are caused by a virus thought to be a potexvirus, the most common ailment being called Necrotic Ring Spot. The symptoms are reddish-brown rings or spots on the leaves. It generally occurs only on the two year leaves of a few rhododendron cultivars such as R. 'Unique', or on Kalmia latifolia. It also appears on the first year foliage of some R. 'Loderi' clones. Little is known about the disease and a does not seem to spread from one cultivar to another. No control is known or generally necessary.

Leaf spotting can also be caused by chemical injury, such as drift from cleaners, paints, or chemicals used to kill moss on roofs as shown in the photo on the right. Sometimes the results of such injury may not show up for weeks or months.

There are a number of leaf spots or burns caused by fungi such as Botrytis cinerea, Pestalotia rhododendri, Phyllosticta, Septoria and others. Many are secondary infections happening after mechanical damage or environmental stress, such as sunburn, drought, winter damage or windburn. They generally occur during wet weather and many times are self limiting with drier weather. Good sanitation is helpful, so remove brown and fallen leaves. Also provide good air circulation. Spraying with Benomyl or similar fungicide can be useful, but is frequently not necessary.

Young Azalea Leafminers, Caloptilia azaleella: (also known as azalea leafroller) larvae tunnel inside leaves and form elongate blotches in April or May. These blotches may resemble leaf spot diseases. Older larvae exit the tunnels, curl the leaf tip and feed inside the curl. Large populations cause the leaves to turn brown and drop from the plant.

Here is a link that might be useful: Rhododendron Culture & Problems

Thank you, rhodyman. I have a feeling the roots are bound and not taking water like they should. I'll try digging up my plants and following the advice you posted. Thank you so much.