Finally getting the oven spring I’ve been chasing for so long

Recipe is as follows:

INGREDIENTS:

• 1050 total flour (950g Caputo "00" Chef's Flour, 75g "Kialla Pure" Organic Stoneground Wholegrain flour, 15g "Bob's red mill" Stoneground Dark Rye flour)

• 250g levain at a 1:2:2 ratio (50g starter, 100g water, 100g flour) fermented until doubled in size and passes float test

• 730ml water

• 26g salt

METHOD:

-Add 700 ml water to flour, mixing until fully combined and allow to autolyse for a couple hours while levain ferments

• Combine levain with dough, dimpling into the surface using the Rubaud method to combine before pouring salt and remaining water into the mix to help incorporate, mixing once more until homogeneous.

• Rest for 15 mins in bowl

• Remove dough from bowl, performing slap and folds on bench until it begins catching air and has a smooth, manageable texture.

• Use a dough scraper to pull the dough into a large rectangle on bench, then fold the top over itself followed by the bottom. Fold the sides in to finish laminating. It should hold its shape. (Not necessary but I think it helps build a lot of strength early on)

• Return to bowl (or split into two bowls if preferable) performing three coil folds at 15 minute intervals, then three more at 30 min intervals. Leave for 2.5 hours or until doubled to finish bulk ferment.

• Gently remove dough and preshape, leaving to sit on counter for 20-30 mins

• Shape and place in bannetons. I like to proof for an hour before covering and placing in fridge for 12 hours or until otherwise time is found to bake.

• To bake, preheat oven to 245°c (475ish f) with dutch oven inside for 45 mins, remove loafs from bannetons onto baking paper, score and place in Dutch oven (I like to use a few ice vubes and lightly spritz with water). Bake covered for 30 mins at 245°C and uncovered at 220°C until desired color is achieved.

If anyone has any tips or advice I'd greatly appreciate it. Im not sure why theres a distinct difference in the crumb of these two loafs, so any pointers would be great!