My first sourdough

I’ve been trying yeast bread for weeks and finally mastered it. Big rise, big ear.

I tried sourdough with my week old starter. But it didn’t rise remotely as much. In fact probably 40% less. And it was quite dense How can I make it rise more? And be lighter

300g white 100g whole meal 2% salt 1% sugar 75% hydration

Mix starter with some water, then add the rest and mix

Mix, fold 3 times in the first 2 hours. Leave over night, banneton and refrigerate. Bake in 8 hours.

Any thoughts?