Pizza Cheese problems, diagnosed

Look at the cheese before changing the oven. Deeply browned, leathery cheese with visible oil usually points to too much heat exposure after the cheese had already melted. Pale cheese sitting in watery puddles points instead to a high-moisture mozzarella mismatch or poor draining. Distinct shreds that soften but do not fuse can point to lower-fat mozzarella or pre-shredded cheese. For most longer home-oven bakes, low-moisture whole-milk mozzarella that you shred yourself is the most predictable baseline; fresh mozzarella is a different ingredient and works best when the pizza style and bake are designed for its higher moisture.