You can run your hand up and down his right chest to find the crop. Feel if it is hard or doughy. You can massage it several times a day as long as it is not puffy/soft, full of liquid. The coconut oil plus drinking water may break up any blockage. Compare his crop to the other’s crops. If his is not empty by morning there may be a blockage. Do you have granite poultry grit out for the chickens to take as needed?