It all sounds food related. You need to try a higher quality grain free food. Do you know of any specific foods they have trouble with? If not, I would start with eliminating chicken, grains and white potato and see if you get any improvement. You could easily have a yeast problem too at this point. I would try Brothers Complete or Natures Variety Instinct. Anal glands producing so much fluid can be due to food intolerances, but the leaking is likely due to all the extra weight and not having a firm enough stool to cause the glands to empty when defecating.
