Urgent, Fish Dieing

[Loko17]

CAN ANYONE HELP, I HAVE 3 GOLDFISH IN A POND OUTSIDE OF MY HOUSE, I JUST WENT OUT TO FEED AND THEY WERE COVERED WITH A WHITE FILM AND WHITE FOAM WAS ON THE SURFACE OF POND. ONE FISH WAS GASPING FOR AIR AT THE SURFACE. ANYONE WHO KNOWS WHAT THIS MIGHT BE PLEASE HELP!!!!!!!!!!!!!!!!!!!!!!

edit:Ok, we've determined the problem. For anyone that has the same problem it may be because of stress on a hot day and low oxygen in the water. my fish are doing great now.