Hiya Pixeyness
Welcome to Aquarium advice from me also:
I would definitely get your water tested as Allivymar suggested, With your fish hanging at the water surface i would say they are having trouble breathing. If your ammonia/nitrites or nitrates are high what this does is clog up the gills and the fish finds it hard to take oxygen from the water so they have to go to the surface for it.
I would do a water change as Alli said because that will help them a bit and hopefully stop your bala from hanging vertical in the water which is another sign that he is finding it hard to breath and he is hanging vertical because he is slowly suffocating and finding it hard to get to the surface.