I have planted some Bitter gourds in my backyard, they get 4-5 hours of morning sunlight each day. I am watering them regularly; once I find the top 2-inches of soil completely dry. Recently I am seeing that veins in the leaves are turning yellow first and then the complete leaf becomes yellow and dies off. I found it could be because of a deficiency of P or K, but I have been fertilizing plants with a balanced fertilizer once every 15 days. I have been using Organic fertilizers, but then I used NPK 19-19-19 chemical fertilizer to see if I get instant results. But I do not see any improvement. I also have at the same time given them Seaweed fertilizer for other micro-nutrients, but no luck yet.