Why is my whole wheat loaf splitting when baking

First time baking a 50% whole wheat and 50% bread flour loaf and both loaves I made split while baking. I felt like I scored them very deep, deeper than my score for regular white bread loaves. I’m a curious as to what could it be. Btw the loaves seem quite well fermented by the time I shaped them and I started a white loaf before the whole wheat and the whole wheat had doubled almost 30 minutes before the white bread one. They were all shaped and put in the fridge at around the same time and the last picture it’s the white loaf I baked between the two whole wheats.

Recipe (1 loaf)

278 g einkorn whole wheat flour

278 g white bread flour

430 g water

120 g water

12 g salt

Method. Mix flour water and starter and rest 40 minutes. continue with 2 sets of stretch and fold 30 minutes in between and followed for 2 sets of coil folds split 30 minutes in between. Bulk fermentation total 6 hours at my house temperature 75 degrees or so. Laminate, pre-shape and bench rest for 20 minutes, laminate again and final shape to the fridge to cold ferment for 20 hours.

Bake in Dutch oven at 450 for 30 minutes, and uncover at 425 for 15 minutes

I can’t show crumb because im taking them to dinner, will update with picture then.