Repeated bouts of diarrhea could be a sign of a greater issue, so you might want to start keeping a diary - make some notes in your calender about when it occurs and how long it lasts. If it´s only diarrhea she may just need worming or change of diet. Worms/parasites go through stages of egg laying and hatching that could cause periodic diarrhea - ask your vet about worming pills. If it´s a food intolerance, you could try switching her to a hypo-allergenic food. There are many out there to choose from. Try what furrypaws suggests and feed her a bland diet for a day or two, then switch (gradually so as not to shock her system) to the hypo-allergenic food and see if that helps. Meanwhile have a good look round your garden to see if there´s anything she might be getting into. If she shows any other symptoms (lethargy, vomiting, blood or parasites in her stool) definitely get her into the vet asap.
BTW, If it turns out to be a parasite, you probably want to have both Kali and Loki wormed at the same time - if they´re littermates you might even want to switch both to the hypo-allergenic food.