PLZ ANSWER! what disease is killing my guppies?!?!?!?

this morning i saw one of my guppies with a tail that was clamped, and her gills were going in and out aalot and hiding behind the heater but the others werre fine. i came home today, and my other fish have the symptoms. i put both fish that are still alive in a hospital tank, but one is near death, and when i took her out and put her in the bowl, she sunk to the bottom, but was still alive. my other one looks like she has a slightly clamped tail, but she is still very active. what disease is this and how can i help save at least one of their lives?