Scales falling off Swordtail

I check my fish daily. I fed them this morning, before I went to work, all my fish were fine. I recently added 2 red velvet swordtails. Both were perfectly fine. I just came home and fed them again. I noticed one of my swordtails sitting on the bottom, tail spilt in half and scales pineconed and falling off. She isn't bloated or anything. I removed her from the tank and put her in a small tank. The other is fine, swimming and eating. What is wrong with the one female.

I have only 2 female swordtails, no male. The only male livebearer in my tank is a large male platy. I looked at the female I took out and she is bloated. Could it be Dropsy?

She was pineconed. Scales were pointing out. I had dropsy affect fish once in awhile... only lost 3 fish from it...

I do not have a Q/T tank yet. I'm planing on upgrading my current 10 gallon to a 20 or 26 bowfront. I will turn the 10 into a Q/T... when given the chance and the money to do so (also have to rearrange whole bed room). I ended up putting the fish down... Didn't want her to suffer. :[ I am taking the fish to Petco to get my money back after work.