Help! I have tried several recipes to make mozzarella, including Kristy Mucci's and each time I've had the same problem. My curds don't seem to be holding together. When I get it to the "strech" stage, it just crumbles in my fingers! I've been careful about keeping the heat to the right level at each stage and the curds look like they are forming correctly, but in the end after I drain them and gently squeeze out the whey, they just crumble when I put them in the hot water. I'm using pasturized (but not ultra-pasturized milk) and liquid vegetable rennet. If anyone can coach me, I'd really appreciate it! I am DETERMINED to make this!