When the temperatures are as high as they have been lately in Orlando (record highs), then all bodies of water grow more bacteria and it makes them smell. You were most likely smelling the lagoon. The wind was probably blowing from the lagoon towards Mels. The lagoon can be treated (they have done it when they had water shows on the lagoon) but it kills fish. When the temperature goes down, the smell will go away. Welcome to Florida and our stinky waterways!