My fish keeps swimming up against the gl, even though i have air pumping into my aquarium...?

I read that is your fish swims up and down against the gl it is trying to get bubbles to breathe, but I have 3 air pumps in my tank. At the back of my 20 gallon tank, i have some air coming out against the wall, but only half of the stick works, then at the front on opposite sides i have an oyster that opens up to release air, and then i also have a small stone that puts up air. I have 2 dalmation mollies, 2 platies, one guppy [i had two but one died today for unknown reasons...anyone know why that might have happened? he wasn't really moving much for the past couple of days, and he liked staying up near the surface of the water] oh, and i have 4 baby fry, maybe 6. those were born about a week ago. my fish doesn't go up against the gl as much as it did, but it still does, and some of my fish just go up and stay at the surface for the water for like a half hour. should i be worried? oh, and my water got pretty cloudy water since the babies came in. my guess that the basteria is just trying to keep up with a sudden change in the bio load. oh, and that guppy that died was only in my tank since saturday. i feed them all brine shrimp, because they seem to eat it more than they did those flakes... i know i have to clean out my rocks soon, because those flakes are still at the bottom of the tank, but not very many...i am really new to fishing, so any advice and help would be GREATLY appreciated. thanks a bunch!