I am new to sourdough baking but have been baking ‘yeast’ bread for 10+ years. I followed Sourdom’s recipe for my starter using white organic flour and rye flour (70:30) in a 100% hydrated starter. After 14 days I was ready to try my first loaf. My ‘old’ baking recipe was 1200 g mixed-grain flour and 600g water plus yeast and a good quantity of seeds and grains so I thought I would stick to this proportion as a familiar starting point. I took 200g of my starter and added 200g flour and 200g filtered rainwater to make a pre-ferment. After about 8 hours I added 900g flour and 300g water and 2 g salt. Mixed in the Kenwood mixer with the dough hook on the slowest setting for a total of about 10 minutes. It seemed very dry and heavy so another 30 grams of water was added and mixed some more. It was turned into a large bowl, oiled and covered with cling wrap to prove for about 10 hours (overnight). In the morning the dough had risen perhaps doubling in volume. It was divided into two and each piece was folded and stretched about 5 times and then places in a container to form. The example shown was formed in a colander lined with well floured linen cloth. After proving for about 7 hours the loaf was turned onto a steel baking tray and placed in the electric oven preheated to 250C with a tray of water underneath and sprayed with water. After 15 minutes the temp was dropped to 200C and sprayed again. Tested after 30 minutes and given another 5 minutes before turning onto a cooling rack. The crust is nice and crusty, with what looks like good colour to me, the aroma is great and the flavour “just like a bought one”. Oven spring was OK, BUT the loaf has not risen as it should and is quite heavy. Help.