hello and welcome.
now i hate to do this to you, but your swords and flagfish (killies) are tropical fish.
so are your danios but are pretty hardy.
also all those fish in a 22L tank, is too many fish.
stick with the mountain minnows.
the white spots are a parasite called ich. you will find PLENTy of info here and on the net on how to get rid of it. I use salt and wunder tonic. it was probably caused cause the swordtails came from tropical water and then went into a coldwater tank... not so good for them, stressed them out, compromised the immune system and BAM you have ich.
if you clean your filter, and I presume it's an internal filter, (let us know what sort) wash the sponge out in the same water as your tank, and replace it.
HTH