Hazel is 5 months old, and tommorow is the day, she is getting spayed. The vet said 5 months was not a problem to do it, but I always use to hear they should be 6 months, is this true? also I'm a little worried about something, Since I have had her, her stool has been excellent, NEVER EVER runny at all, and now today, the day before her surgery, she had MAJOR RUNNY stool, like complete water!! Could this be from the heart pill, which I gave her yesterday???? Please help!