Tiny particles in new tropical aquarium and fish are dying?

Your tank is overstock for the cycling period. That why the guppies and your other fish is dying. So now you should do a 25% water change to clear some amonia from the water. The recomend fish stock during cycling period is one fish per gallon of water so four guppies will be better for your tank. Return the swordtails and let the tank cycle. When you notice all the level are good (A: 0 ppm, Ni: 0 ppm, Na: <25 ppm) then start to add new fish slowly, two or three at a time and get all your fish in within a month. during that time continue to check the water quality.