my betta got that and died to I dont think your other fish can get it but I wouldnt take that chance if it were me. I think it is supposed to be caused from poor water conditions but my bettas water was always kept clean. what are your readings ammonia nitries and nitrates. I will tell you what I done with my betta and he winded up dying anyways once it is noticably it is most of the time to late I put him in a little epsom salt I forgot how much mabey someone here can tell you the amount and pennicillion I am not a vey good speller either. I would try that for about three days and if it didnt show any signs of improvement I would think about putting it down if I were you because it is a awful death I sure dont want to have to go threw that againg watching my fish die and feel so helpless . I am sorry to have to tell you this but I have been threw it before and I know what you are in for.