I doubt it was too much moisture, as they are water lovers. The very fist pic seems like the plant was ok, that little leaf going away is common, on my plants, but you had a new leaf emerging and it looked OK; the other marks were common things I see on my banana plants.
However, one question I had looking at the first pic was how much sun did they receive? Only because it looked kind of shaded.
My other concern would be the fertility of the soil, banana plants are heavy feeders, they will survive in average soils, but for best results it's best to have them in highly fertile, heavily mulched soils.