Bread suddenly not having any oven spring
I've been using the Tartine Country recipe to make some really nice loaves. Then I went to the in-laws for a week over Thanksgiving and left my starter there....I made a new one over a month ago and it has seemed perfectly healthy for several weeks now, but I've never had a good oven spring with it. Everything seems right with the dough, but I can't get the loaf to spring up in those first 20 minutes.
I didn't change anything with my technique - here's some details on my recipe/methods (stock Tartine sourdough if you're familiar):
100g whole wheat flour
900g white flour
750g water
20g salt
200g leaven
Process:
Mix leaven, leave for ~6-8 hours
Mix leaven, flour, 700g water
Wait 20 minutes
Mix salt, 50g water
Wet folds every 30 minutes for ~3-4 hours
Initial shaping - split in half, form two balls
20 minute bench rest
Final shaping - flip over, 4 folds, flip and pull towards you repeatedly
Into the baskets overnight
Preheat 500 degrees F (260 C) with dutch oven inside
Dough into dutch oven, slice slits, drop heat to 450 degrees F (230 degrees C)
20 minutes later remove lid
Cook until brown
Things I've tried:
1. Less bulk rise time (2.5 hours)
2. More bulk rise time (5 hours)
3. Different flours (though this one worked for me in the past)
4. Adding water to the dutch oven for more steam (helped a bit, but not much)
5. Checking oven temperature
Thanks for any tips,
Matt
PS, please see attached the finished (disappointing) product