Use perlite,vermiculite and potting soil are the best. For the yellow leaf try to feed Epsom salt once a month so do liquid Kelp/seaweed fertilizer. For them to bloom use BR-61

What is BR-61? How much Epsom salt?

I would look closer before attacking the issue. Rainy season in Florida usually means rust and/or insects. Can you post pictures of the plant, branch tips, leaves, etc.? I am also unsure if the plants are in containers or in ground and that could make a difference.

BR61 is a "super bloom" type of fertilizer with a high P. Some people use and others don't. If you have it use it but be wary of salt build up in your container plants. Personally if I had any I would only use it on in ground plants where the soil is cooler and P would dissipate over a larger area and not be trapped in the container.

This time of year it’s not unusual for mature plants to drop some of their oldest leaves.

Thanks for all the great advice. I since washed each leaf with a mild soapy solution. They are still prematurely yellowing and falling off, but I did remove whiteflies ! The Plumerias are planted in the ground and receive the east sunlight. I will try fertilizing/feeding this weekend and keep my fingers crossed. Thanks again!

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