I thought the same thing that Teresa did regarding the bad leg thing. If her little tummy is spasming to poo, the rest of her muscles are probably getting overworked as well. Hopefully today will be better for you. Salmon is a fantastic idea, all of our furbabies love it. I know you are working on a special diet, but if you don't mind I would like to throw a couple more ideas into the mix. Plain regular yogurt is really good for their gut and can help the soft stool. Boiling long grain rice and adding it to some boiled chicken, or ground beef is also good. I would boil the ground beef if you use it to get out the extra fat and then mix it with the rice. You can even save the water that you boiled the rice in and add a small amount of lower salt bouillon to it and see if she will drink a bit of it. The starch should help her loose stool. 

Is she on any medications right now? Sometimes meds can have that effect, especially antibiotics. If you cut the supplements for a bit, then try one at a time after her stools are normal, you should be able to either find what it is or rule it out. Maybe just the combo hit her too hard. 

Sending hugs and positive healing energy, hopefully this is short lived and you can get back on track soon!

Jackie and Huckleberry