so *in general* jag's had firm poops the past two weeks or so? If that is the case, then a bit of runny poops once in a while is normal! LOL happens to my dogs on the odd days for no reasons; on other days it's just cuz they had too much food. or a treat that didn't go down all that well. or if they get exercise and poop before their "due time", it's runny cuz the water didn't have enough time to be absorbed by the intestines - had they pooped a few hours later, it would have been firm. I don't know of any humans that have perfect brick poops every single day either, do you?
unless it's constant runny poops, diarrhea, the dog is not feeling well, etc... just take it as it is. remember you are feeding real food, varied food, and you are getting real poop - and it does vary.