I see all kinds of leaf colorations, but other than knowing that a plant is under-potted, and is drying out too quickly in the full sun, I don't know what much of the discoloration means. Sometimes it means the plant needs some Mg, and dosing it/them with a magnesium solution reverses the problem. I just dosed all my plumeria with Mg today in fact. I also just got back from Lowe's and bought 15 large plastic pots, 12" to 16" wide, and I am going to up-pot a bunch of my plumeria later today. I have been watering some of them (in 1 gal. pots) twice a day to keep them hydrated.
I don't know the size of your pots, the media, or the moisture (or lack of moisture) of the media but you might want to get this/those plants out of the sun for some of the hours between 11:00 AM and 4:00 PM. If dehydration is the problem, that will surely help.
