My female damation molly is acting strange. For the past week she has been swimming with her head down and her tail up, and I mean she is at a 90 degree angle to the gravel. She will go and rest up against the filter, heater, wall, and plastic plants, and stay in that odd position. I haven't seen her eat anything, but she does nibble at the gravel, since her head is right there and all. She doesn't have any visible signs of illness so I can't figure out what is wrong. Her tankmates are all fine and are leaving her alone. Any ideas what is wrong, and if there is anything I can do for her? And should I think about a quarintine?