u/BasedKips

After a few (somewhat flat) loaves I’m seeking advice on where I may be going wrong please.

Recipe:
500g bakers flour
400g water
160g starter
30g salt

Process:
- Autolyse 1 hour
- Bulk ferment for 4 hours.
- 4 stretch and folds during the first 2 hrs spaced 30 mins apart
- dough temp at 25-26c throughout bulk ferment.
- shape and put in banneton
- cold proof for about 20 hrs

Photo show end result, Dough at end of bulk and active starter used which was over doubling.

Please help!