It is leaf spot, one of the fungal diseases it is prone to especially in wet humid weather. Most of the time it is tolerated by the tree. Prevention would be to make sure you clean up all of the the infected leaves so there are fewer spores around. Prune the tree to keep it open and provide good air circulation and preventive anti fungal sprays when the weather is conducive to fungal growth.
https://aggie-horticulture.tamu.edu/frui ... immons.pdf
Happy gardening in Hawaii. Gardens are where people grow.