When those trees hit about 10 yrs old, they should start to produce more regularly. It is not uncommon for a tree to rest at any age, but in the first 10 years, I think it needs to rest more, especially with weird climate changes. Dang it, you just might have to settle for chi coo supote or mamay, jack fruit or star fruit, I think you can manage. Eat some spoon meat from a coconut for me, that is my favorite food of all time.