Har and Dane, thank you so much for your suggestions, i suspected there is problem with micro-nutrient deficiency in our garden since we were on solid coral with almost no soil, all the soil had to be imported and it was quite infertile. We are trying to build it up organically with mulch, manure, mycorrhizae, bacteria etc, but seems like it will take time. Will try neem oil spray and work on these specific deficiencies as you suggested.