It's very possible that the problem was in the stretching. I've only made mozz a few times, and I've never been able to stretch it and get it to be shiny and soft like the instructions say. I am using raw whole milk and the cheese is yellow, never white. This time I did get it to stretch a bit, but it wasn't becoming glossy or soft, it was hard and rubbery, so I gave up on trying to stretch it. The flavour was excellent though, so I can live with the texture and the burning in the oven, but of course it would be nice to know what I am doing wrong so as to learn and improve.
I can get some decent store-bought mozzarella di bufala and fior di latte, but even at $5-6 per half gallon of raw milk, it is still cheaper to make my own, and tastes as good or better than the commercial cheese.