Sickly Dogs...

I don't know what it is...but I seem to have dogs that only want to have abnormal bowel movements! I know this is kind of a gross topic; but I'm really not sure what to do. In the spring they were sick off and on with diarrhea, which I come to find out they had hook worm. Now this was complete owner/puppy parenting gone wrong. We forgot to get them heartworm meds and so therefore they were vulnerable to these parasites. Ok, we fixed them up; got them started on heartworm meds and they were good for a little while; then two weeks ago Banya (white female) started having diarrhea again, Panzer (tri-color male) following close behind the next day. This only lasted roughly three days collectively and I'm pretty sure was due to introduction of a new food type. My husband and I thought it'd be nice to have "treat food" canned wet dog food that they get only once in a while. You know to break up the monotony of the same food day in day out :-P
Well...ok not giving canned food anymore; now Panzer is at it again. It is so weird since they are fine ALL WEEK until Thursday (in this case 3 AM Friday morning) and I don't want to call the vet if it's nothing, i.e. the last time. I don't know that he's eaten anything weird in the past 24-48 hours and that's what scares me. How long does it take for food to go through a dog's system (large dogs, Panzer weighs almost 120lbs)? I mean gosh...the dog sitter we had once let them eat plant fertilizer and no harmful effects (needless to say; he is no longer a sitter) but they seem to be prone to this, which is very stressful to say the least! UGH!

**UPDATE** Must have been something he got a hold of...cuz it was over by Friday night! So mysterious...I don't know. Hopefully everything is fine!