Preheat oven to 400 degrees F (200 degrees C). Grease muffin cups or line with muffin liners.Combine flours, sugars, salt and baking powder. Add in milk, banana, and coconut oil and stir until just moistened. Fold in mango and coconut. Divide batter (it will be thick) between 12 muffin tins. They should be filled about ¾ full.Stir together the brown sugar, flour, and coconut for the crumb topping. With a fork, blend in the coconut oil until the mixture is crumbly and the coconut oil is in pea sized pieces. Divide crumble evenly on top of the muffins.Bake for 20 to 25 minutes in the preheated oven, or until a toothpick comes out clean.