Here (CA) they can't take full sun. They get sunburnt.

Could be different in your FL climate with its higher humidity.

Possibly missing vital nutrients such as iron? It's the only thing I can think of.

I'm near Brisbane, Australia. these wouldn't take full sun here either (referring to hoovb's comment) - "zanadu" is about the only thing you see in full sun landscaping, others generally have at least some shelter eg round a palm. "A lot of rain" could mean some nutrient deficiency.
I'm also kind of wondering what that driveway material is - any chance it's leaching something into the soil?

thanks you guys, i never thought of the sun thing, mine are all in mostly shade but this one and others there have grown up in the same spot in the sun so dont think thats it. but thanks. I do agree with the iron defenciancy. Maybe ill give them a good dose of ironite tomorrow. Thanks you guys

i didnt realize zanadu liked full sun, thanks, i have a few in pots kinda tucked away on back deck thinking they were shade lovers. As far as the so called driveway...lol which is actually just a garden path. Its made of washed shell. I dont think that is the problem cause its been processed and everything plus I use it alot for verious other things. Seems to be great for rooting "some" plants or for holding others up when rooting or planting (like plumera cuttings and various cacti) Dont suggest it for putting in bottom of pots for drainage cause it seems to clog up alot.

Shells leach calcium as they decay - I don't think calcium is poisonous in itself but can cause high soil PH and also cause plants to miss out on magnesium, which itself could cause yellowing.

Does that Marl pathway go past the yellow Jacaranda in the background?
That might be your clue that the lime in the shells it locking up iron or other elements in the soil. A Palm or Citrus fertilizer should help correct the deficiency in that case.

Maybe ill give them a good dose of ironite tomorrow.

==>> one might suggest a soil test thru your county extension office ...

PRIOR TO WILLY NILLY LAUNCHING SOIL AMENDMENTS AROUND ...

you are guessing.. why ... ????

i have no doubt about the suggestions made.. these are good peeps... but it is still all speculation ....

===

whats the plants history ... as you note.. if its been growing in sun for a decade ... then i doubt thats the issue ... it doesnt sound like lack of water ... are these supposed to be limbed up ... has it ever been pruned... does it hold its leaves forever ... this MI man has no clue to the answers .. lol ...

what has changed??? is the driveway.. the white stuff new???? etc ...

i wish you luck... but dont waste money.. putting down the wrong thing.. by guessing .. do a soil test ...

ken