i found some good articles on fish Tuberculosis here they are
http://www.4qd.org/Aqua/disease/tb.html
http://www.liveaquaria.com/general/general...ral_pagesid=173
if your fish does have fish tuberculosis be careful because humans can also get this.
ive had the same problem before. what type of filter do u have ? swordtails are small and sometimes get stuck on the filter and it can cause some serious problems like broken spines =[