We had a very similar problem with Summer. She would go for about 3 weeks with semi formed stool (like soft serve ice cream, and it often had mucous in it) and then all of a sudden she would get explosive, watery diarrhea. We had a million tests run- everything short of a biopsy of her intestines, and she was put on many different meds. Everything seemed to work for a short period of time, but she still had bad episodes of diarrhea. We tried many different foods- nutro, solid gold, california natural (that was really bad because I think it is too rich), Eukanuba low residue (prescription food, she did really well on it) and nothing worked. We finally found Eagle Pack Holistic Chicken and Rice and after her first bowl of food, she had the most perfect formed stool. It really was like a miracle for us, after having so many problems for months. We didn't switch her over to Eagle Pack slowly because she was having so many problems any way, that her system was already upset! She has now been on it for about six months and she never had another problem. We now think that she has an intolerance to beef and wheat. It's hard to know if what works for one dog will work for another, but I definitely think its a food intolerance with Lucca. I would stay away from any foods with corn, wheat, soy... and some dogs can't tolerate beef or chicken. It's all trial and error. Get a new bag of food and see what happens. I recommend Eagle Pack because it worked so well for us, but there are lots of great brands out there. Good luck!