My salamander has suddenly lost weight

I have two fire salamanders and I'm starting to get very worried because one of them has always been a little bit skinnier than the other and the larger one has always been a far and happy salamander. But today when I got them out of the tank to clean it, I noticed that she has suddenly become much skinnier than my other salamander. This is an incredibly fast change because just the other day when I was watching them in their pond she was just the same size as she had ever been. It's like it happened over night. The tank is always at 68 degrees and I feed them two to three red worms each every other day. I don't understand why this is happening, does anyone know what this could be?

Could you add a photo of them so we can see? A bit of a long shot, but check the water and tank and see if there are any larvae.

Ok so I checked the tank for larve and couldn't find anything. What's interesting is her belly looks like its back a little bit but it all hangs beneath her instead if being firm so you can only tell its there if she's laying down. You can see her spine all along her body and there are glands behind her head that look swollen too. She was walking very strangely as well today she was almost letting her front legs drag behind her and pushing herself with her back two, when I picked her up though to look at her legs she was using them normally again. I watched her for a while and she would occasionally start to convulse almost as if to throw up and she would look like she was in pain and then she would open her eyes real wide and open her mouth as well and just sit there like that. I'm very worried about her.
I have some pictures below, sorry that they are just links, I'm writing from my phone and most picture hosting sites don't corporate well.

Here is a picture of Sergio (my salamander who is acting normally)
Welcome to Flickr!
And here is Argentina (the abnormal one)
Welcome to Flickr!
Welcome to Flickr!
Welcome to Flickr!

Two thoughts come immediately to mind: (1) Salamanders need to eat more in warmer weather. (2) It's common for one cohabitant to be much more efficient at eating (thus leaving the other animal to dwindle away).

I'd recommend separating them right away, so you can closely monitor who is eating what. I'd also suggest moving them to the coolest possible place in the house, such as a basement or right next to an AC vent. If it's not possible to keep them cool, consider setting up the female in the refrigerator for a few weeks.

I can't really tell much from the photos.

I took her out and put her in a separate container with an ice pack under it to keep it cool. I tried offering her food but she refused to eat so I just dropped in the container with her. After a few minutes though she started turning her head from side to side and then biting at the air. She did this several times she would turn her head to both sides in a sweeping motion and then open her mouth real wide and shut it again quickly. I've never seen either of them do anything like this.