I live in Georgia. I have the same problem. This is what I did. First, I fertilized with high phosphorus fertilizer, but only once. Then, I sprayed anti-fungal/insecticide (organic 3 in 1) on the leaves. I also got a water meter and I test the soil before I water. Finally, I pull the plant under my porch when it is going to rain. My advice, put the plant in a spot that gets as much sun as possible but is under cover, or cover the top of the pot with plastic wrap to keep the rain out. I think this rainy summer in Georgia is just not good for the Plumeria. But, the good news is that my plant is now thriving with less water. I only water whenever the soil gets almost completely dry (or I let the rain water it for me). A word of advice: they also don't like getting completely dry. So, just check the moisture of the soil every other day or so. I can see in your picture that the soil is wet. Honestly, in my opinion, that is the problem -- too much water. Good luck!

Thank you! I have fertilized it already and planted it in new soil. It shot up in May when I did that and has continued since then. I've been letting the rain water it but sometimes, I watered it earlier in the day, without thinking about rain showers (you know how the rain goes here in Georgia). I don't have a cover on the back porch but I can try putting it on the patio table underneath the umbrella and see if that helps.

Will the brown spots go away? Also, what anti-fungal do you use?

I got the same thing with the "photo" option. Instead, I opted for "Houzz photo" and uploaded my photos. Then I inserted them into the post. I hope that helps!

It really shouldn't be a problem if it rains on them every day during the heat of summer. Would you consider changing your soil to a faster draining mix? Even adding 1 part perlite to 3 parts soil would help out.

1:3 is too little. 1:1 or 50% is best even for cactus soils. Most potting soils are designed to hold water and are way too wet for plumerias. At the end of the season, do not worry about leaves. They are being rejected for new growth and will have little effect now. Do not fertilize or spray with bug spray in the heat of the day. This is very hard on the plants. Many spray in the evening and then wash off the leaves in the morning.

Either way please consider changing your soil mix and removing any drainage impediments like saucers. FWIW... what part of GA...hot and humid south or hot and humid north?

I actually replaced the soil in May per the Hall County Extension Office. Mr. Michael Wheeler suggested I try use cactus mix. She has not stopped growing since I changed the soil in May. There are no saucers underneath and there are multiple drainage holes.

I only water in the evening once it has gotten cooler. I do not water during the day (unless it rains). We live in Gainesville (about 47 miles north of Atlanta near the mountains) so it's just hot. There's really no humidity.

Great toubleshooting on your part. I spent alot of time in far southeast Georgia in the 90s. GA is really a nice place.

Thank you! She lost two leaves this weekend but the rest seem to be holding on. I've placed it on our table underneath an umbrella the last few days. She can still get sun but not any rain. The brown spots seem to have stopped appearing.

Gillian, I wanted to let you know that I looked at my Plumeria yesterday and it had new brown spots on the leaves. Really frustrating, but the rest of the plant looks healthy and beautiful (new leaves coming and beautiful blooms). I think tdogdad's comment is probably correct -- that the leaves are weak when the plant is in bloom and the brown spots are nothing to worry about. I think the important thing for your plant is that new leaves are coming and the plant is clearly growing and thriving. I do think watering is a precarious thing with Plumerias. They clearly do like too much water or not enough. I appreciate your comments (and the comments of others) about the soil. When my Plumeria stops blooming, I am going to switch to cactus soil. Good luck with yours.

I planted mine last spring while we were in Virginia and it hasn't bloomed yet. Should I be worried?

Not worried because it is still quite young. freshly rooted plants take on average 2 years to bloom for me. Some sooner and a few stragglers at three years. In my opinion a 1st year bloom is most likely a developing bloom while still as a branch on the parent plant.

Perhaps start with routine fertilizing schedule if you haven't already. I fertilize at half the recommended portion but twice as often therefore there is as steady supply of nutrients for the plants.

What does the rest of the plant look like? Leaves are not the best indicator of problems this time of year.