Thin layer of ice usually forms on the under surface of the wing between the engine and the wing root due to cold fuel which cold soaks the wing.
Definition:Cold soak Can occur in ambient temperatures between −2°C and at least +15°C, ice or frost can form in the presence of visible moisture or high humidity if the aircraft structure remains at 0°C or below.
What you were most likely seeing is the melting ice dripping away. Sometimes On walk arounds in higher temperatures it looks like it raining down there while inspecting the gear.