I have a Red Wag Platy that was exhibiting the same symptoms. I had seen this many times in the past, and it usually meant the fish was a goner. So my wife (who does not take much interest in my fish)informs me that this is her favorite fish. I was about to put the fish out of her misery, but I decided to try to save her. I had some old Amoxicillin capsules in the medicine cabinet, so I took one,opened it up, and mixed it in with some flake food. The platy wasn't eating much, but was trying and sucking a little at the top when I was feeding. So I put some of the flakes/Amoxi combo in there and she ate a little. Of course the other fish did too, but I figured it would be a good idea to treat them as a preventative measure. I fed her twice a day with the amoxi,for about five days, and to my surprise she started gaining weight and straightened out again. She is now fat, healthy, and straight. If I hadn't of seen it myself, I wouldn't have believed it.