I don't remember what they gave him. I think it was a little tiny white pill. He was sick for about 2 days when I took him in (he always gets sick on the weekend). They detected it no problem. I would do another fecal if it's slimy or mucusy - maybe she didn't have it two weeks ago. They said Loki could have even gotten it from the sidewalk!
Also, try Natural Balance Ultra Premium. It's better than the Lamb and Rice one. And feed rice and boiled chicken until the diahrea clears up. Also, so far I am happy with Canidae. It's small kibble that he seems to like and the last 2 times i tried to change his food he got sick the first day (I go REAL slow like 5 pieces of kibble a day literally) but he has not been sick at all from the Canidae. They sent me like 10 sample bags too!
www.canidae.com but that is not the only good one out there.
Edited: I just re-read that you said 2 in one week. I still say try another one!